Bearings, races and components thereof having diamond and other superhard surfaces

ABSTRACT

Diamond bearings and bearing components are disclosed. Some embodiments of the bearings and bearing components include polycrystalline diamond compacts sintered under high pressure and high temperature to create a diamond table chemically and mechanically bonded to a substrate, the diamond table presenting a durable and thermally stable load bearing and articulation surface.

CROSS-REFERENCE TO RELATED APPLICATIONS

This patent application is a continuation of U.S. patent applicationSer. No. 09/840,634 filed on Apr. 22, 2001, and priority is claimedthereto.

BACKGROUND OF THE INVENTION

1. Field of the Invention

Various embodiments of the invention relate primarily to non-planarbearings, bearing components, races, race components, and methods formaking the same. More specifically, some embodiments of the inventioninclude bearings and/or bearing races which have contact, rolling orsliding (or a combination of them) surfaces manufactured in whole or inpart from diamond, cubic boron nitride and other superhard materials.Many types of diamond can be used, including natural diamond,monocrystalline diamond, polycrystalline diamond compacts, and diamondproduced by chemical vapor deposition and physical vapor depositionprocesses. Embodiments of the invention include methods for making,shaping and polishing the diamond portion of the bearing or race,including diamond surfaces thereof. As used generally herein, the term“bearing unit” may include a bearing, race, balls, rollers, cups, cage,bushings, shafts, journals and/or any related components useful forrolling or sliding (or a combination of them) articulation with anotherpart.

2. Description of Related Art

This section will discuss art related to non-planar bearings, bearingcomponents, races, race components.

Various embodiments of this invention relate to the application ofdiamond and other super hard surfaces to bearings and bearing elements.These bearings and bearing elements include both sliding and rollingbearing elements and bearing races. Bearings are an essential part of avast array of mechanical devices. In these various applications,bearings withstand high concentrated forces, direct impact loads, andmust reduce friction and energy loss in mechanical devices. In addition,they must maintain mechanical alignment of parts and maintain precisionand accuracy of mechanical devices. Any bearing application, whether asliding or rolling (or a combination of sliding and rolling) bearing,which is subject to wear, high loads, high maintenance, and/or complexlubrication requirements will benefit from embodiments in the invention.Although embodiments of the invention have other applications as well.

Typical bearing types may include ball bearing with races, rollerbearings with races or tracks, and sliding element bearings. Allbearings may include radial or sleeve type bearings to maintain shaftalignment and thrust bearings to provide for axial force transmission.Roller bearings may perform the same types of functions and can includecylinder rollers, tapered rollers, needle rollers, barrel rollers (bothsymmetrical and asymmetrical). Sliding element bearings may includedevices such as bushings, journals and ball bearing components andconstrained articulating bearing components within mechanical devices.

Materials from which bearing components are fabricated depend upon themechanical requirements for a specific application. Desirable propertiesfor these materials include durability, resistance to fracture and wear,resistance to heat, low coefficient of thermal expansion especiallycompared to typical metals used in bearings, low coefficient of frictionfor sliding contact with no lubricant and affinity for any lubricantswhich may be required to enhance the mechanical operation of thebearing. Various types of lubricants and lubrication systems may be usedto enhance bearing operation and may increase the durability andlongevity of function. The ability to function with little or nolubrication is desirable as lubricants add complexity to bearingsystems.

Lubricants that might be used include; solid media such as graphite,molybdenum, PTFE, powdered media of the same compositions, fluid media,including water, hydrocarbons, fluorocarbons, halogenated hydrocarbons,complex hydrocarbons such as fats and fatty acids, silicone basedlubricants and any other fluid. In some applications, fluids used forlubrication may be abrasive and/or corrosive, such as in oil welldrilling apparatus, or corrosive fluid pumping systems.

Bearings may be called upon to perform many functions in a rotating,articulating or sliding animate or inanimate mechanical devices. Theseinclude, but are not limited to, sustaining high loads, maintainingprecision of alignment, preserving a low coefficient friction formechanical motion and enduring high impact shock loads. In addition,they must perform these various functions often in stressfulenvironments, such as those entailing high temperature and or thepresence of corrosive chemical agents, erosive environments or any otherhostile environment.

An ideal material for bearing application would include having highhardness, high fracture toughness, low coefficient of mechanicalfriction, chemical inertness, thermal stability and high thermalconductivity. Current materials used to produce bearings and racesinclude hard non ferrous alloys, hardened steels, ceramics, plastics(including polyethylene), and crystalline materials such as siliconcarbide, titanium nitride and aluminum oxide. All of these materials arelimited in their utility for this application due to theirsusceptibility to wear, deformation under load, susceptibility tofracture, degradation in corrosive environments and thermal breakdown.

Bearing wear or degradation results in loss of alignment of mechanicalparts leading to further acceleration of wear and or disruption of othermechanical components, increased heat generation, further accelerationof bearing wear, with final catastrophic failure.

The ability of diamond to resistance wear exceeds that of all othermaterials. Further, diamond has desirable thermal stability, thermalconductivity, chemical inertness, and facture toughness to enhancebearing performance. The table below compares properties ofpolycrystalline diamond compact with some other materials from whichbearing surfaces can be made.

TABLE 1 COMPARISON OF DIAMOND TO OTHER MATERIALS Thermal Young's BulkSpecific Hardness Conductivity CTE Modulus Possion's Modulus MaterialGravity (Knoop) (W/m K) (×10⁻⁶ in/in ° C.) (×10⁶ psi) Ratio (×10⁶ psi)Sintered 3.5-4.0   7500-10,400 900-2600 1.0-4.8 120  0.7-0.22 65-82Polycrystalline Diamond Sintered 3.48 3500-4500 800 1.0-4.0 100-1100.20-0.22 55-65 Cubic Boron Nitride Silicon 3.00 2500 84 4.7-5.3  580.17 30 Carbide Aluminum 3.50 2000 8 7.8-8.8 53-55 0.24 34-35 OxideTungsten 14.6 2200 112 6.0 80-90 0.22 48-54 Carbide (10% Co) Cobalt 8.20278-351 11.2-14.3  11-16 33-35 0.293-0.306 27-30 Chrome Ti6Al4V 4.43 3096.6-17.5 11 15-17 0.26-0.36 11-20 Silicon Nitride 3.20 14.2 15.7 1.8-3.727-46  0.2-0.27 15-33

A particular problem with prior art bearings is a tendency to developcatastrophic accelerated wear when a third body wear particle ofsufficient hardness is introduced into the bearing environment.

The failures and pervasive limitations of the prior art show a clearneed for improved bearings, bearing components, races, race components,and methods for making the same.

SUMMARY OF THE INVENTION

Polycrystalline diamond compact is, in many ways, an ideal material forbearing applications. Currently polycrystalline diamond compacts areemployed in the most demanding of mechanical application such as earthboring and rock cutting. Unfortunately, no one has developed thetechnology to fabricate polycrystalline diamond compacts of thisinvention for typical non-planar bearing applications.

It is the object of some embodiments of this invention to providecomponents for non-planar rolling or sliding (or a combination ofrolling and sliding) bearings which have increased wear resistance,decreased coefficient of friction, increased resistance to hostileenvironments and increased ability to sustain high loads and high impactforces without undergoing degradation compared to prior art bearings. Itis a feature of this invention that bearings and/or races are providedthat utilize diamond and other superhard materials in or on theirarticulating surfaces.

It is an object of some preferred embodiments of the invention toprovide bearings and races which can function well in the absence oflubrication or with significantly diminished lubrication compared toprior art bearings used in similar applications. Diamond is known totransfer heat very well and even in its ordinary state, sinteredpolycrystalline diamond exhibits excellent thermal stability. When metallocated in interstitial spaces in polycrystalline diamond compacts isremoved, ability of the part to withstand heat is improved. In someembodiments of the invention, superior thermally stable diamond may becreated by using the processes disclosed in U.S. Pat. Nos. 5,127,923;4,163,769 and 4,104,344, each of which is hereby incorporated byreference.

It is a further object of some embodiments of this invention to providebearings and bearing elements with high chemical and thermal stability,which function in a superior way compared to prior art bearings andsimilar applications. Accordingly, not only do the invented bearings andraces avoid heat buildup because of their low coefficient of frictionand high thermal conductivity, they also resist heat damage due to theirsuperior thermal stability.

It is a further object of some embodiments of this invention to providebearings fabricated with diamond and other superhard materials. Diamondand the other superhard materials of the invention achieve variousobjects stated herein.

It is also an object of some embodiments of the invention to providebearings and races that have a high affinity for lubricants of bothpolar and non polar varieties, with lower frictional losses than priorart bearings and races. Diamond is known to have extremely high surfaceenergy, rendering it very wettable and easy to lubricate. This featureprovides improved utility, durability, and function in the inventeddevices compared to the prior art.

It is a further object of this invention to provide bearings, bearingelements and races with extremely high thermal transfer so that heat maybe transferred away from contact surfaces more efficiently, improvingbearing durability, utility, and longevity. Consequently, bearing lifeis increased and integrity of any lubricants is preserved.

It is a further object of some embodiments of this invention to provideprecision bearings for use and applications where high precision andhigh accuracy are required. The invented bearings and races maintainprecision and accuracy for longer periods due to their extreme low wear,high hardness and high toughness compared to prior art bearings.

It is a further object of some embodiments of this invention to providerotating or rolling bearings of ball, barrel, shaft, sleeve and pintypes, which articulate against races or other counter bearing surfaces,in which at least some of the contact surface is diamond or anothersuperhard material. The diamond or superhard material may be providedacross the entire contact surface or only a portion thereof, such asthrough the use of diamond segments on a contact surface.

It is a further object of some preferred embodiments of this inventionto provide bearings that include rolling elements consisting of eithercontinuous or segmented diamond or other super hard material. Thesebearings and rolling elements may articulate with races or other counterbearing surfaces which are fabricated from non-diamond materials, suchas aluminum oxide, steel, tungsten carbide, silicon carbide, polymers,etc.

It is a further object of some embodiments of this invention to useraces with diamond or other superhard materials articulating againstrolling elements that have non-diamond surfaces, such as aluminum oxide,steel, tungsten carbide, hardened steels, silicon carbide, polymers, andothers.

It is a further object of some preferred embodiments of this inventionto use races that have diamond or other superhard material inlaid onthem in segmented fashion. The diamond or superhard segments may beround or adjacent round nested components, parallelograms, hexagonalcomponents, tetragonal components, radial tetragonal components,combinations of these and other geometries.

It is another object of some preferred embodiments of this invention touse rolling elements which have segmented diamond or other super hardmaterial bearing surfaces including circular or polyhedral geometries.The circular or polyhedral geometries may include strips or veins ofsuperhard material on the surface of the bearing element, the strips orveins being arranged in various desired geometries, such as longitudinalor latitudinal lines, spirals, concentric circles, straight lines, orotherwise.

It is another object of some embodiments of this invention to provideroller bearings for radial and thrust applications consisting ofcylindrical rollers, barrel rollers, asymmetrical barrel rollers andconical section-tapered rollers.

It is another object of some embodiments of this invention to providebearings which are resistant to chemical attack and degradation inhostile environments, such as corrosive or erosive environments. Thenature of diamond and other preferred superhard materials is such thatresistance is provided to hostile environments.

It is another object of some embodiments of this invention to providebearings of geometries that are resistant to fracture under impactloads.

It is another object of some embodiments of this invention to providebearings of geometries that can sustain high loads per unit size withoutdegradation.

It is another object of some embodiments of this invention to providebearings of geometries that can sustain high loads for long servicecycles without significant wear, degradation and accuracy or precision,while maintaining a low coefficient of friction.

It is another object of some embodiments of this invention to providemethods of manufacturing and finishing of bearings, races and bearingcomponents.

It is an object of some embodiments of the invention to providecomponents for bearings having increased wear resistance and a decreasedcoefficient of friction even in the absence of lubricant, thereforemaximizing life of the bearing component. It is a feature of someembodiments of the invention that diamond of various types and othersuperhard materials are used for the bearing surfaces, the superhardmaterials including diamond being very resistant to wear and having avery low coefficient of friction. For the purposes of this document, asuperhard material is a material that has a Knoop hardness of at leastabout 4000. This includes sintered polycrystalline diamond and otherdiamond, diamond-like materials, cubic boron nitride and wurzitic boronnitride.

It is an object of some embodiments of the invention to provide abearing component that does not shed significant amounts of debris orwear particles as a result of use or wear. It is a feature of someembodiments of the invention that polycrystalline diamond compacts orother superhard materials are used to form at least one of thearticulation surfaces of the bearing component, resulting in a lowfriction and long wearing bearing component that sheds little to nodebris or particles during use, and which destroys abrasive third bodieswith minimal or no damage to the bearings.

It is another object of some preferred embodiments the invention to usethe hardest materials known to man, namely diamond, cubic boron nitrideand other superhard materials to give bearing components the highestresistance to wear currently known to man. It is a feature of theinvention that some preferred embodiments use sintered polycrystallinediamond (“PCD”) and sintered polycrystalline diamond compacts (“PDC”)for bearing surfaces. For the purposes of this document, apolycrystalline diamond compact includes a volume of PCD attached to asubstrate material, whether chemically or physically bonded to thesubstrate, or both. The polycrystalline diamond is extremely hard and,when polished, has one of the lowest coefficients of friction of anyknown material. It is a consequent advantage of the invention that thebearing component life far exceeds that of prior art metal and/orceramic bearings. The polycrystalline diamond compact may bemanufactured by a variety of methods, including high pressure and hightemperature sintering in a press, chemical vapor deposition, physicalvapor deposition, and others.

It is an object of some embodiments of the invention to providenon-planar diamond and superhard bearing component surfaces. Variousembodiments of the invention provide novel bearing surfaces that arenon-planar and may be manufactured as polycrystalline diamond compacts.

It is an object of some embodiments of the invention to provide a methodfor manufacturing non-planar polycrystalline diamond compact bearingsurfaces. Various methods are disclosed for materials preparation andpolycrystalline diamond compact manufacturing that will producenon-planar polycrystalline diamond compact bearing surfaces, includingbut not limited to concave and convex spherical bearing surfaces.

It is an object of some embodiments of the invention to provide methodsfor rough shaping of non-planar superhard bearing surfaces. Novelmachining techniques are disclosed which accomplish such shaping.

It is an object of some embodiments of the invention to provide methodsfor finish polishing of non-planar superhard bearing surfaces. Novelpolishing techniques are disclosed which permit polishing of superhardcompact bearing surface to be highly polished to a low coefficient offriction.

The objects, features and advantages of the inventions mentioned aboveare exemplary and illustrative only so that the reader may begin toperceive advantages to be accrued by use of the invention alone or incombination with other technology. Additional objects, features andadvantages of the invention will become apparent to persons of ordinaryskill in the art upon reading the specification and claims and viewingthe drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A depicts a ball bearing element of the invention.

FIG. 1B depicts a cylindrical roller bearing element of the invention.

FIG. 1C depicts a needle roller bearing element of the invention.

FIG. 1D depicts a tapered roller bearing element of the invention.

FIG. 1E depicts a symmetrical barrel roller bearing element of theinvention.

FIG. 1F depicts an asymmetrical barrel roller bearing element of theinvention.

FIGS. 2A-1 and 2A-2 depict a radial ball bearing assembly with inner andouter races and cages.

FIGS. 2B-1 and 2B-2 depict a roller thrust bearing.

FIGS. 2C-1 and 2C-2 depict a ball bearing with a surface volume ofdiamond on a substrate.

FIGS. 2D-1 and 2D-2 depict a ball bearing with segmented bearing insertsor patches on its surface.

FIGS. 2E-1 and 2E-2 depict a ball bearing with segments having a surfaceof polycrystalline diamond compact or other superhard material fixedsecurely into a spherical substrate ball.

FIGS. 2F-1 and 2F-2 depict a ball constructed of polycrystalline diamondor other superhard material.

FIGS. 2G-1 and 2G-2 depict a ball bearing with strips, veins or adiscontinuous pattern of diamond fixed into a substrate ball.

FIGS. 2H, 2H-1 and 2H-2 depict a radial ball bearing assembly.

FIGS. 2K and 2K-1 depict a cylindrical roller bearing assembly.

FIG. 2L-1 and 2L-2 depict a radial ball bearing assembly with radialtetragonal segmented bearing races.

FIGS. 2M-1 and 2M-2 depicts a thrust bearing.

FIGS. 2P-1 and 2P-2 depict a diamond compact insert for the race ofFIGS. 2M-1 and 2M-2.

FIGS. 2Q and 2Q-1 depict a thrust bearing of the invention.

FIGS. 2R-1 and 2R-2 depict a thrust bearing with angular inlaid segmentsof diamond or other superhard material.

FIGS. 2S-1 and 2S-2 depict an angular segment for use in the thrustbearing of FIGS. 2R-1 and 2R-2.

FIGS. 2T-1 and 2T-2 depict a thrust bearing race with multiple circularor oval segment bearing elements inlayed into the appropriate thrustbearing race substrate.

FIGS. 3A-3U depict substrate surface topographical features desirable insome embodiments of the invention.

FIG. 4A depicts a quantity of diamond feedstock adjacent to a metalalloy substrate prior to sintering of the diamond feedstock and thesubstrate to create a polycrystalline diamond compact.

FIG. 4B depicts a sintered polycrystalline diamond compact in which thediamond table, the substrate, and the transition zone between thediamond table and the substrate are shown.

FIG. 4BB depicts a sintered polycrystalline diamond compact in whichthere is a continuous gradient transition from substrate metal throughthe diamond table.

FIG. 4C depicts a substrate prior to use of a CVD or PVD process forform a volume of diamond on the substrate.

FIG. 4D depicts a diamond compact formed by a CVD or PVD process.

FIGS. 5A and 5B depict two-layer substrates useful for making sphericalor partially spherical polycrystalline diamond compacts.

FIGS. 5C-5G depict alternative substrate configurations for makingspherical or partially spherical polycrystalline diamond compacts withcontinuous and segmented bearing surfaces.

FIGS. 6A-1 and 6A-2 depict an assembly useful for making a convexspherical polycrystalline diamond compact.

FIGS. 6B-1 and 6B-2 depict a substrate useful for making concavespherical polycrystalline diamond compacts.

FIG. 7 depicts a device, which may be used for loading diamond feedstockprior to sintering.

FIG. 7A depicts a furnace cycle for removal of a binder material fromdiamond powder or grit feedstock prior to sintering.

FIGS. 8 and 8A depict a precompaction assembly, which may be used toreduce porosity or free space in diamond feedstock prior to sintering.

FIG. 8B depicts anvils of a cubic press that could be used to sinterdiamond.

FIG. 9 depicts EDM rough finishing of a convex spherical part, such as aball bearing.

FIG. 10 depicts EDM rough finishing of a concave spherical part, such asa race or a portion thereof.

FIG. 11 depicts grinding and polishing of a convex spherical part, suchas a ball bearing.

FIG. 12 depicts grinding and polishing of a concave spherical part, suchas a race or a portion thereof.

FIG. 13 depicts a diamond bearing being ground to spherical form anddimensions using a centerless grinding machine.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Reference will now be made to the drawings in which the various elementsof the present invention will be discussed. It will be appreciated thatthe structures and principles of the invention can be applied not onlyto the illustrated examples, but also to many other types ofarticulation surfaces, to the manufacture, shaping and finishing ofsuperhard materials and superhard components, and to the manufacture,shaping and finishing of devices using superhard articulation surfacesand superhard components. Persons skilled in the design of bearingcomponents and other bearing surfaces will understand the application ofthe various embodiments of the invention and their principles to bearingcomponents, bearing surfaces and devices other than those exemplifiedherein.

A. Bearing and Race Structures of the Invention

Below, some preferred bearing and race structures that may be madeaccording to the principles of the invention are described as examples.In later sections of this document, details on appropriate materials formaking the bearings and races, manufacturing, shaping and finishingprocesses are described in greater detail. It will be appreciated tothose accustomed to the art that the structures and principles of theinvention can be applied not only to the specific illustrated examples,but also to other types of articulating surfaces, both sliding androlling bearings, and to the manufacture of super hard materials andsuper hard components for other applications.

FIG. 1A depicts a ball bearing element 101 of the invention.

FIG. 1B depicts a cylindrical roller bearing element 102 of theinvention.

FIG. 1C depicts a needle roller bearing element 103 of the invention.

FIG. 1D depicts a tapered roller bearing element 104 of the invention.

FIG. 1E depicts a symmetrical barrel roller bearing element 105 of theinvention.

FIG. 1F depicts an asymmetrical barrel roller bearing element 106 of theinvention.

Each of the bearing elements 101-106 may be made from solid PCD, apolycrystalline diamond compact, or other diamond or superhardmaterials, as desired.

FIGS. 2A-1 and 2A-2 depict a radial ball bearing assembly 107 with innerand outer race cages. An outer race 1, and inner race 3, a bearingrolling ball element 2 and a cage 4 to contain the bearings inside thebearing assembly while articulating are depicted. Contact surfaces ofthe balls 2 or the races 1 and 3 may be diamond or superhard material inwhole or in part.

FIGS. 2B-1 and 2B-2 depict a roller thrust bearing. Bearing rolling ballelements 6 roll and articulate with races 5 and 7 and the bearing cage8. Contact surfaces of the balls or the races may be diamond orsuperhard material in whole or in part.

FIG. 2C-1 and 2C-2 depict a ball bearing 109. The ball bearing 109depicted may be a polycrystalline diamond compact that includes asurface volume of diamond 9 on a substrate 10. This embodiment includesa continuous surface layer of diamond, although the diamond surface maybe discontinuous as well. The substrate may be any suitable substrate asdescribed elsewhere herein.

Some embodiments of the invention may include a surface volume ofpolycrystalline diamond compact, diamond applied through vapordeposition means (such as chemical vapor deposition or physical vapordeposition), polycrystalline cubic boron nitride compact or other superhard material. The surface volume of diamond or superhard material maybe applied to an appropriate durable substrate, which may include anappropriate durable metal, ceramic material, composite material, orcrystalline material. In one preferred implementation the surface layerconsists of polycrystalline diamond compact applied to a metallicsubstrate. This means that the diamond is chemically bonded to thesubstrate to provide an extremely hard low friction durable long lastingarticulating surface for the bearing. In bearing applications thesurface geometry would be finished to a suitable precision and accuracyconducive to smooth glass like finish with a very low coefficient offriction. Diamond is extremely hard and possesses an extremely lowcoefficient of friction. Consequently, when diamond is used, the wearbetween the surface layer of diamond and any part which it articulatesagainst would be negligible over time resulting in an extremely longlasting durable part. In addition, because of the extreme toughness ofthe diamond surface on metal substrate constructed as a compact, therolling bearing element has extremely high fracture toughness making itdesirable as a bearing element where peak loads and impacts areexperienced as part of duty cycle.

FIGS. 2D-1 and 2D-2 depict a ball bearing 110 with bearing inserts 11 onthe surface 12 to form a discontinuous diamond surface. The inserts 11may be located on the substrate material with great precision andaccuracy. The bearing surface of the ball bearing depicted may bedivided into areas of diamond or other superhard material separate byveins of substrate material. Fabrication of balls with this vein andpatch structure (such as a polyhedral or round segmented surface) offersome advantages to the manufacturing process for certain substratemetals as well as provide some advantages in high impact situations.Each bearing segment of diamond or superhard material independentlyaccommodate transient deformations under peak load without resulting infracture of the segments of diamond or superhard material.

FIGS. 2E-1 and 2E-2 depicts a cross-sectional view of a ball bearing 111with plugs 14. The plugs 14 may be a polycrystalline diamond compacthaving a surface of polycrystalline diamond or other superhard material.The plugs 14 may be fixed securely into receptacles on sphericalsubstrate ball 15 or other desired structure. The plugs or segments maybe fashioned as polycrystalline diamond compacts or other superhardmaterial. Each plug may be a continuous phase of superhard material, ora compact formed from a bearing surface of superhard material on asubstrate, such as a polycrystalline diamond compact. The plugs may bebonded, welded, or mechanically fastened to the substrate structure,preferably in an appropriate receptacle, leaving the superhard bearingsurface exposed. High quality curvilinear and spherical surface finishesthat are obtained by terminal finishing processes described later inthis document. This approach to segmented bearing surfaces permits thefabrication of extremely large spherical and or curvilinear bearingsurfaces not possible with continuous bearing surfaces. Size limitationsin the manufacturing of polycrystalline diamond compact elements mightotherwise prevent manufacture of such large bearing elements.

FIGS. 2F-1 and 2F-2 depict a ball 112 constructed of solid or continuousphase polycrystalline diamond or other superhard material. This ball 112is made of solid diamond or superhard material without a separatesubstrate. The ball 112 has a continuous phase of diamond throughout itsinterior. Embodiments of such a continuous phase bearing element may bemade from polycrystalline diamond, polycrystalline cubic boron nitride,or other superhard material. This structure has certain advantages froma chemical electromagnetic and structural standpoint.

FIGS. 2G-1 and 2G-2 depict a ball bearing 113 with strips, veins or adiscontinuous pattern of diamond 17 or another superhard materiallocated on a substrate 18. The diamond on the ball 113 surface may be ina regular or irregular discontinuous pattern in any desired geometry,such a concentric circles, spirals, latitudinal or longitudinal lines orotherwise. This structure possesses some of the advantages common to thesegmented bearing surface described above.

FIGS. 2H, 2H-1 and 2H-2 depict a radial ball bearing assembly 114. FIG.2 j depicts another cross sectional view at 2 j-2 j of the bearing 114of FIG. 2 i. The bearing assembly 114 includes an outer race 20 and aninner race 22, each of which may have continuous diamond or othersuperhard articulating surfaces 21. Various manufacturing technologiescan be used to apply a diamond layer to bearing surfaces, includingdirect fabrication of PDC at the race surfaces, chemical vapordeposition and physical vapor deposition. Additionally, where needed ordesired, the inner race, outer race or both may be fabricated entirelyof PDC structure. When the race is PDC, the roller bearing element mayalso be PDC or it may be another superhard material or anothernon-superhard material.

FIGS. 2K and 2K-1 depict a cylindrical roller bearing assembly 127. Thebearing assembly 127 includes inner race 33, outer race 34 andcylindrical bearing member 35. Cylindrical bearing member 35 includes asubstrate and an outer superhard articulation surface 37. The bearingmember 35 turns in a sleeve 36 with a superhard articulation surface.The sleeve and bearing member are held buy a retainer 38.

FIGS. 2L-1 and 2L-2 depict a radial ball bearing assembly 115 withradial tetragonal segmented bearing races. Radial tetragonal segmentedbearing surfaces 23 are shown having a superhard bearing surface. Innerrace 151 is depicted and ball bearings 150 are shown. Either the ballbearing elements or the tetragonal segmented bearing surfaces or bothmay be made from diamond or other superhard materials. Use of individualbearing surfaces such as tetragonal segments provides an advantage froma manufacturing standpoint. In some manufacturing environments, it maybe easier and cheaper to make individual PDC or superhard segments andlater assemble them on an appropriate substrate as the bearing surfaceof a race, rather than making the entire bearing surface of the race asa unitary PDC or superhard component.

FIGS. 2M-1 and 2M-2 depict a thrust bearing race 116 with a segmenteddiamond other superhard material bearing surface present in round nestedinlays 28 (circular segments) on a substrate. The nested inlays 27 areformed to each have an arcuate depression 27 therein. Each of the inlaysmay be made as a polycrystalline diamond compact having a volume ofdiamond on its own substrate. The inlays may be installed on a substratein nested juxtaposition. Alternatively, the inlays may be made from acontinuous phase of material. For some bearing applications and somemanufacturing environments, it may be easier and cheaper to manufactureinlays and assemble them on a substrate than to form the entire bearingsurface as a unitary component.

FIGS. 2P-1 and 2P-2 depicts an individual bearing segment that may beused in an application such as that depicted in the previous figures.The segment 119 includes a volume of diamond 123 c or other superhardmaterial on a substrate 121, although the segment 119 could be formedfrom a continuous phase of superhard material. The geometry of thesegment 119 depicted is generally circular with a concave arcuatesection 122 to accommodate nesting with other segments and present acontinuous bearing surface 120. The sides of the segment 119 as shown bynumerals 123 a and 123 b are generally parallel but are not square withthe bearing surface or bottom 123 d or the segment 119 to provide abetter fit and grip with adjacent segments in a bearing or race.

FIGS. 2Q and 2Q-1 depict a thrust bearing 124 with continuous diamond 24or other superhard material bonded to a substrate 25.

FIGS. 2R-1 and 2R-2 depict a thrust bearing 125 with angular inlaidsegments 29 using diamond or other superhard material. Each angularinlayed race bearing segment or element 29 is juxtaposed to adjacentbearing elements and fixed suitably, such as by brazing to the thrustbearing substrate 31. Each segment 29 may be a continuous phase ofsuperhard material or it may include a layer of superhard material 32 ona substrate 30, such as a polycrystalline diamond compact.

FIGS. 2 v and 2 w depict a front and side view of a single angularsegment 29 for use in the bearing of FIGS. 2 t and 2 u or otherapplications. The bearing segment 29 has angular sides 29 a and 29 b forinlaying on a substrate in juxtaposition with other bearing segments.The top 29 c and bottom 29 d edges of the bearing segment 29 aredepicted as being arcuate but may be configured otherwise. The segment29 may be a continuous phase of superhard material or it may include avolume of superhard material 29 e on a substrate 29 f such as in apolycrystalline diamond compact.

FIGS. 2S-1 and 2S-2 depict an angular segment 29 for use in a bearing.The bearing segment 29 has angular sides 29 a and 29 b for inlaying on asubstrate in juxtaposition with other bearing segments. The top 29 c andbottom 29 d edges of the bearing segment 29 are depicted as beingarcuate but may be configured otherwise. The segment 29 may be acontinuous phase of superhard material or it may include a volume ofsuperhard material 29 e on a substrate 29 f such as in a polycrystallinediamond compact.

FIGS. 2T-1 and 2T-2 depict a thrust bearing race 126 with multiplesegmented bearing elements 31 inlayed into the appropriate thrustbearing race substrate 32. The bearing elements 31 may be circular,oval, or any other desired shape. The bearing elements may bepolycrystalline diamond compacts, continuous phase polycrystallinediamond, other continuous phase superhard material, or superhardmaterial on a substrate. The bearing elements 31 may be affixed to thesubstrate 32 by an appropriate technique, such as brazing, bonding,cementing, pressing, welding, mechanical fit, mechanical attachment orotherwise. The bearing elements 31 may be directly adjacent each otherto provide a continuous superhard bearing surface, or they may be spacedapart so that veins of substrate 31 exist between them.

One purpose of this invention to incorporate diamond and or other superhard materials onto the bearing surfaces of the rolling elements and orraces in various geometries in order to improve the durability,reliability, and precision of mechanical devices incorporating bearingelements. In addition, implementation of the inventive concepts shoulddiminish susceptibility to degradation of mechanical function ofbearings and/or races in corrosive environments, increase resistance towear, diminish the requirements for complex lubricating systems as partof bearing units and increase resistance to a high loads and to impactloads.

Bearings made using the inventive concepts and preferred materials maybe made with excellent thermal and dimensional stability and excellentcorrosion resistance, and having a low coefficient of friction andextreme resistance to wear and dimensional degradation.

The invented structures and methods may be applied to an infinitevariety of bearings and races and bearing and articulation surfaces inany field. Some additional examples of products that may be madeaccording to the inventive concepts include radial ball bearings, radialroller bearings, ball thrust bearings, roller thrust bearings, bushings,sleeves, races, and any other articulation surface.

Some embodiments of the invention that include a diamond table on one ofthe articulation surfaces, the diamond table will typically be fromsubmicron thickness to about 3000 microns thick or more. Someembodiments of the invention utilize a solid polycrystalline diamondcomponent, such as a solid polycrystalline diamond ball or a solidpolycrystalline diamond socket. In those cases, the diamond tabledimension will equal the component dimension.

For ball and socket bearing components using a polycrystalline diamondcompact with a substrate, it is expected that for ease of manufacturing,the polycrystalline diamond table will be from less than about 5 micronsthick to more than about 2 millimeters thick in the most preferredembodiments of the invention. Other diamond bearing component surfacesand other superhard bearing surfaces might have thickness in the rangeof less than about 1 micron to more than about 100 microns, or solidpolycrystalline diamond components could be used as described above.

In various embodiments of the invention, the geometry and dimensions ofthe bearing surface of the component may be designed to meet the needsof a particular application and may differ from that which is describedherein.

B. Attachment of Diamond in the Preferred Bearing component

1. Nature of the Diamond-Substrate Interface

In the preferred embodiment of the invention, a polycrystalline diamondcompact provides unique chemical bonding and mechanical grip between thearticulation surface and the substrate material.

Some preferred bearing component structures of the invention uses apolycrystalline diamond compact for at least one of the bearing and racecomponents. A bearing or race component which utilizes polycrystallinediamond compact will have a chemical bond between substrate material andthe diamond crystals. The result of this structure is an extremelystrong bond between the substrate and the diamond table.

A method by which PDC is preferably manufactured is described later inthis document. Briefly, it involves sintering diamond crystals to eachother, and to a substrate under high pressure and high temperature. Inthe most preferred embodiment, the finished part will have residualstresses at the diamond to substrate interface that do not exceed thetensile strength of the substrate, the diamond or the diamond tosubstrate interface.

FIGS. 4A and 4B illustrate the physical and chemical processes involvedmanufacturing polycrystalline diamond compacts.

In FIG. 4A, a quantity of diamond feedstock 430 (such as diamond powderor crystals) is placed adjacent to a metal-containing substrate 410prior to sintering. In the region of the diamond feedstock 430,individual diamond crystals 431 may be seen, and between the individualdiamond crystals 431 there are interstitial spaces 432. If desired, aquantity of solvent-catalyst metal may be placed into the interstitialspaces 432.

The substrate 410 may be a suitable pure metal or alloy, 2 or moremetals or alloys, a composite structure of metals and alloys, or acemented carbide containing a suitable metal or alloy as a cementingagent such as cobalt-cemented tungsten carbide. Preferably the substratewill be a metal with high tensile strength. When the residual stressesin the finished part at the diamond to substrate interface that do notexceed the tensile strength of the substrate, the diamond or the diamondto substrate interface, the result is a very strong and durablecomponent. Contributing to this is the use of a substrate that willexpand during the sintering process and contract at the conclusion ofsintering to yield a substrate in the finished part that isdimensionally 0.01% to 1.0% smaller than it was prior to sintering.

The illustration shows the individual diamond crystals and thecontiguous metal crystals in the metal substrate. The interface 420between diamond powder and substrate material is a critical region wherebonding of the diamond table to the substrate must occur. In someembodiments of the invention, a boundary layer of a third materialdifferent than the diamond and the substrate is placed at the interface420. This interface boundary layer material, when present, may serveseveral functions including, but not limited to, enhancing the bond ofthe diamond table to the substrate, and mitigation of the residualstress field at the diamond-substrate interface.

Once diamond powder or crystals and substrate are assembled as shown inFIG. 4A, the assembly is subjected to high pressure and high temperatureas described later herein in order to cause bonding of diamond crystalsto diamond crystals and to the substrate. The resulting structure ofsintered polycrystalline diamond table bonded to a substrate is called apolycrystalline diamond compact (PDC). A compact, as the term is usedherein, is a composite structure of two different materials, such asdiamond crystals, and a substrate metal. The analogous structureincorporating cubic boron nitride crystals in the sintering processinstead of diamond crystals is called polycrystalline cubic boronnitride compact (PCBNC). Many of the processes described herein for thefabrication and finishing of PDC structures and parts work in a similarfashion for PCBNC. In some embodiments of the invention, PCBNC may besubstituted for PDC.

FIG. 4B depicts a polycrystalline diamond compact 401 after the highpressure and high temperature sintering of diamond feedstock to asubstrate. Within the PDC structure, there is an identifiable volume ofsubstrate 402, an identifiable volume of diamond table 403, and atransition zone 404 between diamond table and substrate containingdiamond crystals and substrate material. Crystalline grains of substratematerial 405 and sintered or bonded crystals of diamond 406 aredepicted.

On casual examination, the finished compact of FIG. 4B will appear toconsist of a solid table of diamond 403 attached to the substrate 402with a discrete boundary. On very close examination, however, atransition zone 404 between diamond table 403 and substrate 402 can becharacterized. This zone represents a gradient interface between diamondtable and substrate with a gradual transition of ratios between diamondcontent and metal content. The composition of the transition zone willrange from low diamond content at the substrate side to nearly purediamond at the nearly pure diamond at the sintered diamond side. Thepresence of such a transition zone distributes the stress between thediamond table and the substrate.

In the transition zone where diamond crystals and substrate metal areintermingled, chemical bonds are formed between the diamond and metal.From the transition zone 404 into the diamond table 403, the metalconcentration diminishes and is limited to solvent-catalyst metal thatfills the three-dimensional vein-like structure of interstitial voids oropenings 407 within the sintered diamond table structure 403. Thesolvent-catalyst metal found in the voids or openings 407 may have beenswept up from the substrate during sintering or may have beensolvent-catalyst metal added to the diamond feedstock before sintering.

During the sintering process, there are three types of chemical bondsthat are created: diamond-to-diamond bonds, diamond-to-metal bonds, andmetal-to-metal bonds. In the diamond table, there are diamond-to-diamondbonds (sp₃ carbon bonds) created when diamond particles partiallysolvate in the solvate-catalyst metal and then are bonded together. Inthe substrate and in the diamond table, there are metal-to-metal bondscreated by the high pressure and high temperature sintering process. Andin the transition zone, diamond-to-metal bonds are created betweendiamond and solvent-catalyst metal.

The combination of these various chemical bonds and the mechanical gripexerted by solvent-catalyst metal in the diamond table such as in theinterstitial spaces of the diamond structure diamond table provideextraordinarily high bond strength between the diamond table and thesubstrate. Interstitial spaces are present in the diamond structure andthose spaces typically are filled with solvent-catalyst metal, formingveins of solvent-catalyst metal within the polycrystalline diamondstructure. This bonding structure contributes to the extraordinaryfracture toughness of the compact, and the veins of metal within thediamond table act as energy sinks halting propagation of incipientcracks within the diamond structure. The transition zone and metal veinstructure provide the compact with a gradient of material propertiesbetween those of the diamond table and those of substrate material,further contributing to the extreme toughness of the compact. Thetransition zone can also be called an interface, a gradient transitionzone, a composition gradient zone, or a composition gradient, dependingon its characteristics. The transition zone distributesdiamond/substrate stress over the thickness of the zone, reducing zonehigh stress of a distinct linear interface. The subject residual stressis created as pressure and temperature are reduced at the conclusion ofthe high pressure/high temperature sintering process due to thedifference in pressure and thermal expansive properties of the diamondand substrate materials.

The diamond sintering process occurs under conditions of extremely highpressure and high temperature. According to the inventors' bestexperimental and theoretical understanding, the diamond sinteringprocess progresses through the following sequence of events. A pressurecell containing feedstock of unbonded diamond powder or crystals(diamond feedstock) and a substrate is heated to a temperature above themelting point of the binder metal of the substrate 410 and flows orsweeps into the interstitial voids 407 between the adjacent diamondcrystals 406. It diffuses under the driving forces of the pressuredifferential to fill the voids as well as being pulled in by the surfaceenergy or capillary action of the large surface area of the diamondcrystals 406. As the temperature continues to rise, carbon atoms fromthe surface of diamond crystals dissolve into this interstitial moltenmetal, forming a carbon solution.

At the proper threshold of temperature and pressure, diamond becomes thethermodynamically favored crystalline allotrope of carbon. As thesolution becomes super saturated with respect to C_(d) (carbon diamond),carbon from this solution begins to crystallize as diamond onto thesurfaces of diamond crystals bonding adjacent diamond crystals togetherwith diamond-diamond bonds into a sintered polycrystalline diamondstructure 406. The interstitial metal fills the remaining void spaceforming the vein-like lattice structure 407 within the diamond table bycapillary forces and pressure driving forces. Because of the crucialrole that the interstitial metal plays in forming a solution of carbonatoms and reducing the activation energy for the solution/precipitationreaction in which the polycrystalline diamond structure is formed, themetal is referred to as a solvent-catalyst metal.

FIG. 4BB depicts a polycrystalline diamond compact having both substratemetal 480 and diamond 481, but in which there is a continuousconcentration gradient or transition 482 from substrate metal todiamond. In such a compact, the gradient transition zone may be theentire compact or a portion of it.

In some embodiments of the invention, a quantity of solvent-catalystmetal may be combined with the diamond feedstock prior to sintering.This is found to be necessary when forming thick PCD tables, solid PDCstructures, or when using multimodal fine diamond where there is littleresidual free space within the diamond powder. In each of these cases,there is insufficient ingress of solvent-catalyst metal via the sweep ordiffusion mechanism to adequately mediate the sintering process as asolvent-catalyst. The metal may be added by direct addition of powder,or by generation of metal powder in situ with an attritor mill or by thewell-known method of chemical reduction of metal salts deposited ondiamond crystals. Added metal may constitute any amount from less than1% by mass, to greater than 35%. This added metal may consist of thesame metal or alloy as is found in the substrate, or may be a differentmetal or alloy selected because of its material and mechanicalproperties. Example ratios of diamond feedstock to solvent-catalystmetal prior to sintering include mass ratios of 70:30, 85:15, 90:10, and95:15.

When sintering diamond on a substrate with an interface boundary layer,no solvent-catalyst metal from the substrate is available to sweep intothe diamond table and participate in the sintering process. In thiscase, the boundary layer material, if composed of a suitable material,metal or alloy that can function as a solvent-catalyst, may serve as thesweep material mediating the diamond sintering process. In other caseswhere the desired boundary material cannot serve as a solvent-catalyst,a suitable amount of solvent-catalyst metal powder as described hereinis added to the diamond crystal feed stock as described above. In theabsence of a substrate metal source, the solvent-catalyst metal for thediamond sintering process must be supplied entirely from the added metalpowder. The boundary material bonds chemically to the substratematerial, and bonds chemically to the diamond table and/or the addedsolvent-catalyst metal in the diamond table. The remainder of thesintering and fabrication process are the same as with the conventionalsolvent-catalyst sweep sintering and fabrication process.

For the sake of simplicity and clarity in this patent, the substrate,transition zone, and diamond table have been discussed as distinctlayers. However, it is important to realize that the finished sinteredobject consists of a composite structure characterized by a continuousgradient transition from substrate material to diamond table rather thanas distinct layers with clear and discrete boundaries, hence the term“compact”.

In addition to the sintering processes described above, diamond partssuitable for use as bearings for such applications may also befabricated as solid polycrystalline diamond structures without asubstrate. These are formed by placing the diamond powder combined witha suitable amount of added solvent-catalyst metal powder as describedabove in a refractory metal can (typically Ta, Nb, Zr, or Mo) with ashape approximating the shape of the final part desired. This assemblyis then taken through the sintering process. However, in the absence ofa substrate metal source, the solvent-catalyst metal for the diamondsintering process must be supplied entirely from the added metal powder.After processing in the high pressure high temperature press andfinishing, bearings thus formed may be used as is, or bonded to metalsubstrates to function as total bearing component articulations.

Sintering is the preferred method of creating a diamond table with astrong and durable bond to a substrate material. Other methods ofproducing a diamond table bonded to a substrate are possible. Atpresent, these typically are not as strong or durable as thosefabricated with the sintering process. It is also possible to use thesemethods to form diamond structures directly onto substrates suitable foruse as bearing component bearings. A table of polycrystalline diamondeither with or without a substrate may be manufactured and laterattached to a bearing component in a location such that it will form abearing surface. The attachment could be performed with any suitablemethod, including welding, brazing, sintering, diffusion welding,diffusion bonding, inertial welding, adhesive bonding, or the use offasteners such as screws, bolts, or rivets. In the case of attaching adiamond table without a substrate to another object, the use of suchmethods as brazing, diffusion welding/bonding or inertia welding may bemost appropriate.

2. Alternative Methods for Creating a Diamond Bearing Surface

Although high pressure/high temperature sintering is the preferredmethod for creating a diamond bearing surface, other methods forproducing a volume of diamond may be employed as well. For example,either chemical vapor deposition (CVD), or physical vapor deposition(PVD) processes may be used. CVD produces a diamond layer by thermallycracking an organic molecule and depositing carbon radicals on asubstrate. PVD produces a diamond layer by electrically causing carbonradicals to be ejected from a source material and to deposit on asubstrate where they build a diamond crystal structure. The CVD and PVDprocesses have some advantages over sintering. Sintering is performed inlarge, expensive presses at high pressure (such as 40-68 kilobars) andat high temperatures (such as 1200 to 1500 degrees Celsius). It isdifficult to achieve and maintain desired component shape using asintering process because of deformation and flow of high pressuremediums used and possible deformation of substrate materials.

In contrast, CVD and PVD take place at atmospheric pressure or lower, sothere no need for a pressure medium and there is no deformation ofsubstrates.

Another disadvantage of sintering is that it is difficult to achievesome geometries in a sintered polycrystalline diamond compact. When CVDor PVD are used, however, the gas phase used for carbon radicaldeposition can completely conform to the shape of the object beingcoated, making it easy to achieve a desired non-planar shape.

Another potential disadvantage of sintering polycrystalline diamondcompacts is that the finished component will tend to have large residualstresses caused by differences in the coefficient of thermal expansionand modulus between the diamond and the substrate. While residualstresses can be used to improve strength of a part, they can also bedisadvantageous. When CVD or PVD is used, residual stresses can beminimized because CVD and PVD processes do not involve a significantpressure transition (such from about 40-68 Kbar to atmospheric pressurein high pressure and high temperature sintering) during manufacturing.

Another potential disadvantage of sintering polycrystalline diamondcompacts is that few substrates have been found that are suitable forsintering. In the prior art, the typical substrate used was tungstencarbide. In the invention, non-planar components have been made usingother substrates. When CVD or PVD are used, however, synthetic diamondcan be placed on many substrates, including titanium, most carbides,silicon, molybdenum and others. This is because the temperature andpressure of the CVD and PVD coating processes are low enough thatdifferences in coefficient of thermal expansion and modulus betweendiamond and the substrate are not as critical as they are in a hightemperature and high pressure sintering process.

A further difficulty in manufacturing sintered polycrystalline diamondcompacts is that as the size of the part to be manufactured increases,the size of the press must increase as well. Sintering of diamond willonly take place at certain pressures and temperatures, such as thosedescribed herein. In order to manufacture larger sinteredpolycrystalline diamond compacts, ram pressure of the press (tonnage)and size of tooling (such as dies and anvils) must be increased in orderto achieve the necessary pressure for sintering to take place. Butincreasing the size and capacity of a press is more difficult thansimply increasing the dimensions of its components. There may be apractical physical size constraints on press size due to themanufacturing process used to produce press tooling.

Tooling for a press is typically made from cemented tungsten carbide. Inorder to make tooling, the cemented tungsten carbide is sintered in avacuum furnace followed by pressing in a hot isosatic press (“HIP”)apparatus. Hipping must be performed in a manner that maintains uniformtemperature throughout the tungsten carbide in order to achieve uniformphysical qualities and quality. These requirements impose a practicallimit on the size tooling that can be produced for a press that isuseful for sintering polycrystalline diamond compacts. The limit on thesize tooling that can be produced also limits the size press that can beproduced.

CVD and PVD manufacturing apparatuses may be scaled up in size with fewlimitations, allowing them to produce polycrystalline diamond compactsof almost any desired size.

CVD and PVD processes are also advantageous because they permit precisecontrol of the thickness and uniformity of the diamond coating to beapplied to a substrate. Temperature is adjusted within the range of 500to 1000 degrees Celsius, and pressure is adjusted in a range of lessthan 1 atmosphere to achieve desired diamond coating thickness.

Another advantage of CVD and PVD processes is that they allow themanufacturing process to be monitored as it progresses. A CVD or PVDreactor can be opened before manufacture of a part is completed so thatthe thickness and quality of the diamond coating being applied to thepart may be determined. From the thickness of the diamond coating thathas already been applied, time to completion of manufacture can becalculated. Alternatively, if the coating is not of desired quality, themanufacturing processes may be aborted in order to save time and money.

In contrast, sintering of polycrystalline diamond compacts is performedas a batch process that cannot be interrupted, and progress of sinteringcannot be monitored. The pressing process must be run to completion andthe part may only be examined afterward.

CVD is performed in an apparatus called a reactor. A basic CVD reactorincludes four components. The first component of the reactor is one ormore gas inlets. Gas inlets may be chosen based on whether gases arepremixed before introduction to the chamber or whether the gases areallowed to mix for the first time in the chamber. The second componentof the reactor is one or more power sources for the generation ofthermal energy. A power source is needed to heat the gases in thechamber. A second power source may be used to heat the substratematerial uniformly in order to achieve a uniform coating of diamond onthe substrate. The third component of the reactor is a stage or platformon which a substrate is placed. The substrate will be coated withdiamond during the CVD process. Stages used include a fixed stage, atranslating stage, a rotating stage and a vibratory stage. Anappropriate stage must be chosen to achieved desired diamond coatingquality and uniformity. The fourth component of the reactor is an exitport for removing exhaust gas from the chamber. After gas has reactedwith the substrate, it must be removed from the chamber as quickly aspossible so that it does not participate in other reactions, which wouldbe deleterious to the diamond coating.

CVD reactors are classified according to the power source used. Thepower source is chosen to create the desired species necessary to carryout diamond thin film deposition. Some CVD reactor types includeplasma-assisted microwave, hot filament, electron beam, single, doubleor multiple laser beam, arc jet and DC discharge. These reactors differin the way they impart thermal energy to the gas species and in theirefficiency in breaking gases down to the species necessary fordeposition of diamond. It is possible to have an array of lasers toperform local heating inside a high pressure cell. Alternatively, anarray of optical fibers could be used to deliver light into the cell.

The basic process by which CVD reactors work is as follows. A substrateis placed into the reactor chamber. Reactants are introduced to thechamber via one or more gas inlets. For diamond CVD, methane (CH₄) andhydrogen (H₂) gases are preferably brought into the chamber in premixedform. Instead of methane, any carbon-bearing gas in which the carbon hassp₃ bonding may be used. Other gases may be added to the gas stream inorder to control quality of the diamond film, deposition temperature,gain structure and growth rate. These include oxygen, carbon dioxide,argon, halogens and others.

The gas pressure in the chamber is preferably maintained at about 100torr. Flow rates for the gases through the chamber are preferably about10 standard cubic centimeters per minute for methane and about 100standard cubic centimeters per minute for hydrogen. The composition ofthe gas phase in the chamber is preferably in the range of 90-99.5%hydrogen and 0.5-10% methane.

When the gases are introduced into the chamber, they are heated. Heatingmay be accomplished by many methods. In a plasma-assisted process, thegases are heated by passing them through a plasma. Otherwise, the gasesmay be passed over a series of wires such as those found in a hotfilament reactor.

Heating the methane and hydrogen will break them down into various freeradicals. Through a complicated mixture of reactions, carbon isdeposited on the substrate and joins with other carbon to formcrystalline diamond by sp₃ bonding. The atomic hydrogen in the chamberreacts with and removes hydrogen atoms from methyl radicals attached tothe substrate surface in order to create molecular hydrogen, leaving aclear solid surface for further deposition of free radicals.

If the substrate surface promotes the formation of sp₂ carbon bonds, orif the gas composition, flow rates, substrate temperature or othervariables are incorrect, then graphite rather than diamond will grow onthe substrate.

There are many similarities between CVD reactors and processes and PVDreactors and processes. PVD reactors differ from CVD reactors in the waythat they generate the deposition species and in the physicalcharacteristics of the deposition species. In a PVD reactor, a plate ofsource material is used as a thermal source, rather than having aseparate thermal source as in CVD reactors. A PVD reactor generateselectrical bias across a plate of source material in order to generateand eject carbon radicals from the source material. The reactor bombardsthe source material with high energy ions. When the high energy ionscollide with source material, they cause ejection of the desired carbonradicals from the source material. The carbon radicals are ejectedradially from the source material into the chamber. The carbon radicalsthen deposit themselves onto whatever is in their path, including thestage, the reactor itself, and the substrate.

Referring to FIG. 4C, a substrate 440 of appropriate material isdepicted having a deposition face 441 on which diamond may be depositedby a CVD or PVD process. FIG. 4D depicts the substrate 440 and thedeposition face 441 on which a volume of diamond 442 has been depositedby CVD or PVD processes. A small transition zone 443 is present in whichboth diamond and substrate are located. In comparison to FIG. 4B, it canbe seen that the CVD or PVD diamond deposited on a substrate lacks themore extensive gradient transition zone of sintered polycrystallinediamond compacts because there is no sweep of solvent-catalyst metalthrough the diamond table in a CVD or PVD process.

Both CVD and PVD processes achieve diamond deposition by line of sight.Means (such as vibration and rotation) are provided for exposing alldesired surfaces for diamond deposition. If a vibratory stage is to beused, the bearing surface will vibrate up and down with the stage andthereby present all bearing surfaces to the free radical source.

There are several methods, which may be implemented in order to coatcylindrical objects with diamond using CVD or PVD processes. If a plasmaassisted microwave process is to be used to achieve diamond deposition,then the object to receive the diamond must be directly under the plasmain order to achieve the highest quality and most uniform coating ofdiamond. A rotating or translational stage may be used to present everyaspect of the bearing surface to the plasma for diamond coating. As thestage rotates or translates, all portions of the bearing surface may bebrought directly under the plasma for coating in such a way to achievesufficiently uniform coating.

If a hot filament CVD process is used, then the bearing surface shouldbe placed on a stationary stage. Wires or filaments (typically tungsten)are strung over the stage so that their coverage includes the bearingsurface to be coated. The distance between the filaments and the bearingsurface and the distance between the filaments themselves may be chosento achieve a uniform coating of diamond directly under the filaments.

Diamond bearing surfaces can be manufactured by CVD and PVD processeither by coating a substrate with diamond or by creating a freestanding volume of diamond, which is later mounted for use. A freestanding volume of diamond may be created by CVD and PVD processes in atwo-step operation. First, a thick film of diamond is deposited on asuitable substrate, such as silicon, molybdenum, tungsten or others.Second, the diamond film is released from the substrate.

As desired, segments of diamond film may be cut away, such as by use ofa Q-switched YAG laser. Although diamond is transparent to a YAG laser,there is usually a sufficient amount of sp₂ bonded carbon (as found ingraphite) to allow cutting to take place. If not, then a line may bedrawn on the diamond film using a carbon-based ink. The line should besufficient to permit cutting to start, and once started, cutting willproceed slowly.

After an appropriately-sized piece of diamond has been cut from adiamond film, it can be attached to a desired object in order to serveas a bearing surface. For example, the diamond may be attached to asubstrate by welding, diffusion bonding, adhesion bonding, mechanicalfixation or high pressure and high temperature bonding in a press.

Although CVD and PVD diamond on a substrate do not exhibit a gradienttransition zone that is found in sintered polycrystalline diamondcompacts, CVD and PVD process can be conducted in order to incorporatemetal into the diamond table. As mentioned elsewhere herein,incorporation of metal into the diamond table enhances adhesion of thediamond table to its substrate and can strengthen the polycrystallinediamond compact. Incorporation of diamond into the diamond table can beused to achieve a diamond table with a coefficient of thermal expansionand compressibility different from that of pure diamond, andconsequently increasing fracture toughness of the diamond table ascompared to pure diamond. Diamond has a low coefficient of thermalexpansion and a low compressibility compared to metals. Therefore thepresence of metal with diamond in the diamond table achieves a higherand more metal-like coefficient of thermal expansion and the averagecompressibility for the diamond table than for pure diamond.Consequently, residual stresses at the interface of the diamond tableand the substrate are reduced, and delamination of the diamond tablefrom the substrate is less likely.

A pure diamond crystal also has low fracture toughness. Therefore, inpure diamond, when a small crack is formed, the entire diamond componentfails catastrophically. In comparison, metals have a high fracturetoughness and can accommodate large cracks without catastrophic failure.Incorporation of metal into the diamond table achieves a greaterfracture toughness than pure diamond. In a diamond table havinginterstitial spaces and metal within those interstitial spaces, if acrack forms in the diamond and propagates to an interstitial spacecontaining metal, the crack will terminate at the metal and catastrophicfailure will be avoided. Because of this characteristic, a diamond tablewith metal in its interstitial spaces is able to sustain much higherforces and workloads without catastrophic failure compared to purediamond.

Diamond-diamond bonding tends to decrease as metal content in thediamond table increases. CVD and PVD processes can be conducted so thata transition zone is established. However, it is preferred for thebearing surface to be essentially pure polycrystalline diamond for lowwear properties.

Generally CVD and PVD diamond is formed without large interstitialspaces filled with metal. Consequently, most PVD and CVD diamond is morebrittle or has a lower fracture toughness than sintered polycrystallinediamond compacts. CVD and PVD diamond may also exhibit the maximumresidual stresses possible between the diamond table and the substrate.It is possible, however, to form CVD and PVD diamond film that has metalincorporated into it with either a uniform or a functionally gradientcomposition.

One method for incorporating metal into a CVD or PVD diamond film it touse two different source materials in order to simultaneously depositthe two materials on a substrate in a CVD of PVD diamond productionprocess. This method may be used regardless of whether diamond is beingproduced by CVD, PVD or a combination of the two.

Another method for incorporating metal into a CVD diamond film chemicalvapor infiltration. This process would first create a porous layer ofmaterial, and then fill the pores by chemical vapor infiltration. Theporous layer thickness should be approximately equal to the desiredthickness for either the uniform or gradient layer. The size anddistribution of the pores can be sued to control ultimate composition ofthe layer. Deposition in vapor infiltration occurs first at theinterface between the porous layer and the substrate. As depositioncontinues, the interface along which the material is deposited movesoutward from the substrate to fill pores in the porous layer. As thegrowth interface moves outward, the deposition temperature along theinterface is maintained by moving the sample relative to a heater or bymoving the heater relative to the growth interface. It is imperativethat the porous region between the outside of the sample and the growthinterface be maintained at a temperature that does not promotedeposition of material (either the pore-filling material or undesiredreaction products). Deposition in this region would close the poresprematurely and prevent infiltration and deposition of the desiredmaterial in inner pores. The result would be a substrate with openporosity an poor physical properties.

Another alternative manufacturing process that may be used to producebearing surfaces and components of the invention involves use of energybeams, such as laser energy, to vaporize constituents in a substrate andredeposit those constituents on the substrate in a new form, such as inthe form of a diamond coating. As an example, a metal, polymeric orother substrate may be obtained or produced containing carbon, carbidesor other desired constituent elements. Appropriate energy, such as laserenergy, may be directed at the substrate to cause constituent elementsto move from within the substrate to the surface of the substrateadjacent the area of application of energy to the substrate. Continuedapplication of energy to the concentrated constituent elements on thesurface of the substrate can be used to cause vaporization of some ofthose constituent elements. The vaporized constituents may then bereacted with another element to change the properties and structure ofthe vaporized constituent elements.

Next, the vaporized and reacted constituent elements (which may bediamond) may be diffused into the surface of the substrate. A separatefabricated coating may be produced on the surface of the substratehaving the same or a different chemical composition than that of thevaporized and reacted constituent elements. Alternatively, some of thechanged constituent elements which were diffused into the substrate maybe vaporized and reacted again and deposited as a coating on the. Bythis process and variations of it, appropriate coatings such as diamond,cubic boron nitride, diamond like carbon, B₄C, SiC, TiC, TiN, TiB, cCN,Cr₃C₂, and Si₃N₄ may be formed on a substrate.

In other manufacturing environments, high temperature laser application,electroplating, sputtering, energetic laser excited plasma deposition orother methods may be used to place a volume of diamond, diamond-likematerial, a hard material or a superhard material in a location in whichwill serve as a bearing surface.

In light of the disclosure herein, those of ordinary skill in the artwill comprehend the apparatuses, materials and process conditionsnecessary for the formation and use of high quality diamond on asubstrate using any of the manufacturing methods described herein inorder to create a diamond bearing surface.

Manufacturing the Diamond Portion of Preferred Structures

This section provides information related to manufacturing somepreferred structures of the invention. The principles discussed hereinmay be applied to manufacture nearly any type of bearing surface.

The Nature of the Problem

In areas outside of bearing components, in particular in the field ofrock drilling cutters, polycrystalline diamond compacts have been usedfor some time. Historically those cutters have been cylindrical in shapewith a planar diamond table at one end. The diamond surface of a cutteris much smaller than the bearing surface needed in most bearingcomponents. Thus, polycrystalline diamond cutter geometry andmanufacturing methods are not directly applicable to bearing components.

The particular problem posed by the manufacture of a bearing componentis how to produce a polycrystalline diamond compact with a complexshape, such as concave or convex spherical, cylindrical, etc. Fordiscussion purposes herein, manufacture of concave and convex sphericalparts is primarily discussed. In the manufacture of a sphericalpolycrystalline diamond compact, symmetry becomes a dominantconsideration in performing loading, sealing, and pressing/sinteringprocedures. The spherical component design requires that pressures beapplied radially in making the part. During the high pressure sinteringprocess, described in detail below, all displacements must be along aradian emanating from the center of the sphere that will be produced inorder to achieve the spherical geometry. To achieve this in hightemperature/high pressure pressing, an isostatic pressure field must becreated. During the manufacture of such spherical parts, if there is anydeviatoric stress component, it will result in distortion of the partand may render the manufactured part useless.

Special considerations that must be taken into account in makingspherical polycrystalline diamond compacts are discussed below.

Modulus

Most polycrystalline diamond compacts include both a diamond table and asubstrate. The material properties of the diamond and the substrate maybe compatible, but the high pressure and high temperature sinteringprocess in the formation of a polycrystalline diamond compact may resultin a component with excessively high residual stresses. For example, fora polycrystalline diamond compact using tungsten carbide as thesubstrate, the sintered diamond has a Young's modulus of approximately120 million p.s.i., and cobalt cemented tungsten carbide has a modulusof approximately 90 million p.s.i. Modulus refers to the slope of thecurve of the stress plotted against the stress for a material. Modulusindicates the stiffness of the material. Bulk modulus refers to theratio of isostatic strain to isostatic stress, or the unit volumereduction of a material versus the applied pressure or stress.

Because diamond and most substrate materials have such a high modulus, avery small stress or displacement of the polycrystalline diamond compactcan induce very large stresses. If the stresses exceed the yieldstrength of either the diamond or the substrate, the component willfail. The strongest polycrystalline diamond compact is not necessarilystress free. In a polycrystalline diamond compact with optimaldistribution of residual stress, more energy is required to induce afracture than in a stress free component. Thus, the difference inmodulus between the substrate and the diamond must be noted and used todesign a component that will have the best strength for its applicationwith sufficient abrasion resistance and fracture toughness.

b. Coefficient of Thermal Expansion

The extent to which diamond and its substrate differ in how they deformrelative to changes in temperature also affects their mechanicalcompatibility. Coefficient of thermal expansion (“CTE”) is a measure ofthe unit change of a dimension with unit change in temperature or thepropensity of a material to expand under heat or to contract whencooled. As a material experiences a phase change, calculations based onCTE in the initial phase will not be applicable. It is notable that whencompacts of materials with different CTE's and moduluses are used, theywill stress differently at the same stress.

Polycrystalline diamond has a coefficient of thermal expansion (as aboveand hereafter referred to as “CTE”) on the order of 24 micro inches perinch (10⁻⁵ inches) of material per degree (□ in/in° C.). In contrast,carbide has a CTE on the order of 6-8 □in/in° C. Although these valuesappear to be close numerically, the influence of the high moduluscreates very high residual stress fields when a temperature gradient ofa few hundred degrees is imposed upon the combination of substrate anddiamond. The difference in coefficient of thermal expansion is less of aproblem in prior art cylindrical polycrystalline diamond compacts with aplanar diamond table than in the manufacture of spherical components orcomponents with other complex geometries for bearing components. When aspherical polycrystalline diamond compact is manufactured, differencesin the CTE between the diamond and the substrate can cause high residualstress with subsequent cracking and failure of the diamond table, thesubstrate or both at any time during or after high pressure/hightemperature sintering.

c. Dilatoric and Deviatoric Stresses

The diamond and substrate assembly will experience a reduction of freevolume during the sintering process. The sintering process, described indetail below, involves subjecting the substrate and diamond assembly topressure ordinarily in the range of about 40 to about 68 kilobar. Thepressure will cause volume reduction of the substrate. Some geometricaldistortion of the diamond and/or the substrate may also occur. Thestress that causes geometrical distortion is called deviatoric stress,and the stress that causes a change in volume is called dilatoricstress. In an isostatic system, the deviatoric stresses sum to zero andonly the dilatoric stress component remains. Failure to consider all ofthese stress factors in designing and sintering a polycrystallinediamond component with complex geometry (such as concave and convexspherical polycrystalline diamond compacts) will likely result infailure of the process.

d. Free Volume Reduction of Diamond Feedstock

As a consequence of the physical nature of the feedstock diamond, largeamounts of free volume are present unless special preparation of thefeedstock is undertaken prior to sintering. It is necessary to eliminateas much of the free volume in the diamond as possible, and if the freevolume present in the diamond feedstock is too great, then sintering maynot occur. It is also possible to eliminate the free volume duringsintering if a press with sufficient ram displacement is employed. Isimportant to maintain a desired uniform geometry of the diamond andsubstrate during any process which reduces free volume in the feedstock,or a distorted or faulty component may result.

e. Selection of Solvent-Catalyst Metal

Formation of synthetic diamond in a high temperature and high pressurepress without the use of a solvent-catalyst metal is not a viable methodat this time. A solvent-catalyst metal is required to achieve desiredcrystal formation in synthetic diamond. The solvent-catalyst metal firstsolvates carbon preferentially from the sharp contact points of thediamond feedstock crystals. It then recrystallizes the carbon as diamondin the interstices of the diamond matrix with diamond-diamond bondingsufficient to achieve a solid. That solid distributed over the substratesurface is referred to herein as a polycrystalline diamond table. Thesolvent-catalyst metal also enhances the formation of chemical bondswith substrate atoms.

A preferred method for adding the solvent-catalyst metal to diamondfeedstock is by causing it to sweep from the substrate that containssolvent-catalyst metal during high pressure and high temperaturesintering. Powdered solvent-catalyst metal may also be added to thediamond feedstock before sintering, particularly if thicker diamondtables are desired. An attritor method may also be used to add thesolvent-catalyst metal to diamond feedstock before sintering. If toomuch or too little solvent-catalyst metal is used, then the resultingpart may lack the desired mechanical properties, so it is important toselect an amount of solvent-catalyst metal and a method for adding it todiamond feedstock that is appropriate for the particular part to bemanufactured.

f. Diamond Feedstock Particle Size and Distribution

The wear characteristics of the finished diamond product are integrallylinked to the size of the feedstock diamond and also to the particledistribution. Selection of the proper size(s) of diamond feedstock andparticle distribution depends upon the service requirement of thespecimen and also its working environment. The wear resistance ofpolycrystalline diamond is enhanced if smaller diamond feedstockcrystals are used and a highly diamond-diamond bonded diamond table isachieved.

Although polycrystalline diamond may be made from single modal diamondfeedstock, use of multi-modal feedstock increases both impact strengthand wear resistance. The use of a combination of large crystal sizes andsmall crystal sizes of diamond feedstock together provides a part withhigh impact strength and wear resistance, in part because theinterstitial spaces between the large diamond crystals may be filledwith small diamond crystals. During sintering, the small crystals willsolvate and reprecipitate in a manner that binds all of the diamondcrystals into a strong and tightly bonded compact.

9. Diamond Feedstock Loading Methodology

Contamination of the diamond feedstock before or during loading willcause failure of the sintering process. Great care must be taken toensure the cleanliness of diamond feedstock and any addedsolvent-catalyst metal or binder before sintering.

In order to prepare for sintering, clean diamond feedstock, substrate,and container components are prepared for loading. The diamond feedstockand the substrate are placed into a refractory metal container called a“can” which will seal its contents from outside contamination. Thediamond feedstock and the substrate will remain in the can whileundergoing high pressure and high temperature sintering in order to forma polycrystalline diamond compact. The can will preferably be sealed byelectron beam welding at high temperature and in a vacuum.

Enough diamond aggregate (powder or grit) is loaded to account forlinear shrinkage during high pressure and high temperature sintering.The method used for loading diamond feedstock into a can for sinteringaffects the general shape and tolerances of the final part. Inparticular, the packing density of the feedstock diamond throughout thecan should be as uniform as possible in order to produce a good qualitysintered polycrystalline diamond compact structure. In loading, bridgingof diamond can be avoided by staged addition and packing.

The degree of uniformity in the density of the feedstock material afterloading will affect geometry of the polycrystalline diamond compact.Loading of the feedstock diamond in a dry form versus loading diamondcombined with a binder and the subsequent process applied for theremoval of the binder will also affect the characteristics of thefinished polycrystalline diamond compact. In order to properlypre-compact diamond for sintering, the pre-compaction pressures shouldbe applied under isostatic conditions.

h. Selection of Substrate Material

The unique material properties of diamond and its relative differencesin modulus and CTE compared to most potential substrate materialsdiamond make selection of an appropriate polycrystalline diamondsubstrate a formidable task. When the additional constraints ofbiocompatibility is placed on the substrate, the choice is even moredifficult. Most biocompatible metals are not compatible with thematerial properties of synthetic diamond. A great disparity in materialproperties between the diamond and the substrate creates challengessuccessful manufacture of a polycrystalline diamond component with theneeded strength and durability. Even very hard substrates appear to besoft compared to polycrystalline diamond. The substrate and the diamondmust be able to withstand not only the pressure and temperature ofsintering, but must be able to return to room temperature andatmospheric pressure without delaminating, cracking or otherwisefailing. Further, even among those materials that are believed to bebiocompatible, it is expedient to use only those which meet governmentalregulatory guidelines for products such as bearing components.

Selection of substrate material also requires consideration of theintended application for the part, impact resistance and strengthsrequired, and the amount of solvent-catalyst metal that will beincorporated into the diamond table during sintering. Substratematerials must be selected with material properties that are compatiblewith those of the diamond table to be formed.

i. Substrate Geometry

In the invention, it is preferred to manufacture spherical,hemispherical, partially spherical, arcuate and other complex concaveand convex geometries of polycrystalline diamond compacts, which maylater be cut, machined and otherwise finished to serve as heads, cup orraces, other bearing component surfaces, other bearing surfaces, andother wear-resistant surfaces. Formation of such parts requiresconsideration of the unique geometry of the substrate. In particular,the spherical geometry of the desired finished product requires thatforces applied to the substrate and diamond feedstock during sinteringbe along a radian emanating from the center of the sphere to beproduced.

Further, it is important to consider whether to use a substrate whichhas a smooth surface or a surface with topographical features. Substratesurfaces may be formed with a variety of topographical features so thatthe diamond table is fixed to the substrate with both a chemical bondand a mechanical grip. Use of topographical features on the substrateprovides a greater surface area for chemical bonds and with themechanical grip provided by the topographical features, can result in astronger and more durable component.

2. Preferred Materials and Manufacturing Processes

The inventors have discovered and determined materials and manufacturingprocesses for constructing the preferred polycrystalline diamondcompacts for use in a bearing component. It is also possible tomanufacture the invented bearing surfaces by methods and using materialsother than those listed below.

The steps described below, such as selection of substrate material andgeometry, selection of diamond feedstock, loading and sintering methods,will affect each other, so although they are listed as separate stepsthat must be taken to manufacture a polycrystalline diamond compact, nostep is completely independent of the others, and all steps must bestandardized to ensure success of the manufacturing process.

Select Substrate Material

In order to manufacture any polycrystalline diamond component, anappropriate substrate should be selected. For the manufacture of apolycrystalline diamond component to be used in a bearing component, theinventors prefer use of the substrates listed in the table below.

TABLE 2 SOME SUBSTRATES FOR BEARING APPLICATIONS SUBSTRATE ALLOY NAMEREMARKS Titanium Ti6/4 (TiAIVa) A thin tantalum barrier is ASTM F-1313(TiNbZr) preferably placed on the ASTM F-620 titanium substrate beforeASTM F-1580 loading diamond feedstock. TiMbHf Nitinol (TiNi + other)Cobalt chrome ASTM F-799 Contains cobalt, chromium and molybdenum.Wrought product. Cobalt chrome ASTM F-90 Contains cobalt, chromium,tungsten and nickel. Cobalt chrome ASTM F-75 Contains cobalt, chromiumand molybdenum. Cast product. Cobalt chrome ASTM F-562 Contains cobalt,chromium, molybdenum and nickel. Cobalt chrome ASTM F-563 Containscobalt, chromium, molybdenum, tungsten, iron and nickel. Tantalum ASTMF-560 (unalloyed) Refractory metal. Platinum various Niobium ASTM F-67(unalloyed) Refractory metal. Maganese Various May include Cr, Ni, Mg,molybdenum. Cobalt cemented tungsten WC carbide Cobalt chrome cementedCoCr cemented WC tungsten carbide Cobalt chrome cemented CoCr cementedCrC chrome carbide Cobalt chrome cemented CoCr cemented SiC siliconcarbide Fused silicon carbide SiC Cobalt chrome molybdenum CoCrMo A thintungsten or tungsten/cobalt layer is placed on the substrate beforeloading diamond feedstock. Stainless steel Various

The CoCr used is preferably either CoCrMo or CoCrW. The precedingsubstrates are examples only. In addition to these substrates, othermaterials may be appropriate for use as substrates for construction ofbearing components and other bearing surfaces.

When titanium is used as the substrate, it is sometimes preferred by theinventors to place a thin tantalum barrier layer on the titaniumsubstrate. The tantalum barrier prevents mixing of the titanium alloyswith cobalt alloys used in the diamond feedstock. If the titanium alloysand the cobalt alloys mix, it possible that a detrimentally low meltingpoint eutectic inter-metallic compound will be formed during the highpressure and high temperature sintering process. The tantalum barrierbonds to both the titanium and cobalt alloys, and to the polycrystallinediamond that contains cobalt solvent-catalyst metals. Thus, apolycrystalline diamond compact made using a titanium substrate with atantalum barrier layer and diamond feedstock that has cobaltsolvent-catalyst metals can be very strong and well formed.Alternatively, the titanium substrate may be provided with an alpha caseoxide coating, an oxidation layer or an oxide composite forming abarrier which prevents formation of a eutectic metal.

If a cobalt chrome molybdenum substrate is used, it is preferred toplace either a thin tungsten layer or a thin tungsten and cobalt layeron the substrate before loading of the diamond feedstock in order tocontrol formation of chrome carbide (CrC) during sintering.

In addition to those listed, other appropriate substrates may be usedfor forming polycrystalline diamond compact bearing surfaces. Further,it is possible within the scope of the invention to form a diamondbearing surface for use without a substrate. It is also possible to forma bearing surface from any of the superhard materials and other bearingmaterials listed herein, in which case a substrate may not be needed.Additionally, if it is desired to use a type of diamond or carbon otherthan polycrystalline diamond, substrate selection may differ. Forexample, if a diamond bearing surface is to be created by use ofchemical vapor deposition or physical vapor deposition, then use of asubstrate appropriate for those manufacturing environments and for thecompositions used will be necessary.

In some embodiments of the invention, the difference in physicalproperties of the substrate and the diamond layer will result insubstantial expansion of the substrate during the sintering process andsubsequent shrinkage of the substrate at the conclusion of sintering.Consequently, after sintering, in some instances the substrate may be0.01% to 1.0% smaller in dimension that it was prior to sintering, Sucha result can provide the beneficial effect of the substrate pulling awayfrom the diamond table as desired in some applications, such as abearing cup. Or it can result in residual stresses between the substrateand the diamond table which, if managed correctly, strengthen thefinished part.

Determination of Substrate Geometry

1. General Substrate Configuration

A substrate geometry appropriate for the compact to be manufactured andappropriate for the materials being used should be selected. In order tomanufacture a concave spherical cup or race or a convex spherical headas preferred in some embodiments of the invention, it is necessary toselect a substrate geometry that will facilitate the manufacture ofthose parts. In order to ensure proper diamond formation and avoidcompact distortion, forces acting on the diamond and the substrateduring sintering must be strictly radial. Therefore the preferredsubstrate geometry at the contact surface with diamond feedstock formanufacturing an cup or race, a head, or any other spherical componentis generally spherical.

As mentioned previously, there is a great disparity in the materialcharacteristics of synthetic diamond and most available substratematerials. In particular, modulus and CTE are of concern. But whenapplied in combination with each other, some substrates can form astable and strong spherical polycrystalline diamond compact. The tablebelow lists physical properties of some preferred substrate materials.

TABLE 3 MATERIAL PROPERTIES OF SOME PREFERRED SUBSTRATES YOUNG'S BULKSUBSTRATE MODULUS MODULUS CTE MATERIAL (×10⁶ psi) (×10⁶ psi) (×10⁶ in/in° C.) Ti 6/4 15-17 11-20 5.4 CoCrMo 33-35 27-30 16.9 CoCrW 35.5 35 16.3

Use of either titanium or cobalt chrome substrates alone for themanufacture of spherical polycrystalline diamond compacts may result incracking of the diamond table or separation of the substrate from thediamond table. In particular, it appears that titanium's dominantproperty during high pressure and high temperature sintering iscompressibility while cobalt chrome's dominant property during sinteringis CTE. In some embodiments of the invention, a substrate of two or morelayers may be used in order to achieve dimensional stability during andafter manufacturing.

Referring to the table below, some combinations of substrate materialsthat may be used for making spherical polycrystalline diamond compactsare listed.

TABLE 4 SPHERICAL SUBSTRATE COMBINATIONS FOR MAKING CONVEX PCD SPHERESSUBSTRATE SUBSTRATE CORE SHELL REMARKS Ti 6/4 ASTM F-136 sphere CoCrASTM F-799 Alpha case oxide coating on titanium or tantalum barrierlayer on titanium. Ti 6/4 ASTM F-136 sphere CoCr ASTM F-90 Alpha caseoxide coating on titanium or tantalum barrier layer on titanium. CoCrASTM F-799 sphere Ti 6/4 ASTM F-136 Tantalum barrier layer on titanium.CoCr ASTM F-90 sphere Ti 6/4 ASTM F-136 Tantalum barrier layer ontitanium. CoCr ASTM F-799 sphere None Substrate surface topographicalfeatures used, as described below. Al₂O₃ ceramic core sphere None

The alpha case oxide coating is used to seal the titanium from reactingwith the cobalt chrome. The tantalum barrier layer can be in the rangeof about 0.002 to 0.010 inches thick with 0.008 believed to be optimal.

A two piece substrate as mentioned above may be used to achievedimensional stability in spherical parts. A two piece substrate mayovercome differences in CTE and modulus between diamond and thesubstrate. It appears that use of a substrate with a plurality of layersovercomes the tendencies of the materials to expand and contract atdifferent rates, which if not addressed will cause cracking of thediamond.

A spherical substrate having at least two distinct layers of differentsubstrate materials can be employed to stabilize the component andprevent the substrate from shrinking away from the diamond table, thusresulting in the successful manufacture of spherical polycrystallinediamond compacts.

Referring to FIGS. 5A-5F, various substrate structures of the inventionfor making a generally spherical polycrystalline diamond compact aredepicted. FIGS. 5A and 5B depict two-layer substrates.

In FIG. 5A, a solid first sphere 501 of a substrate material intended tobe used as the substrate shell or outer layer was obtained. Thedimensions of the first sphere 501 are such that the dimension of thefirst sphere 501 with a diamond table on its exterior will approximatethe intended dimension of the component prior to final finishing. Oncethe first sphere 501 of the substrate is obtained, a hole 502 is boredinto its center. The hole 502 is preferably bored, drilled, cut, blastedor otherwise formed so that the terminus 503 of the hole 502 ishemispherical. This is preferably achieved by using a drill bit or endmill with a round or ball end having the desired radius and curvature.

Then a second sphere 504 of a substrate material is obtained. The secondsphere 504 is smaller than the first sphere 501 and is be placed in hole502 in the first sphere 501. The substrates materials of spheres 501 and504 are preferably selected form those listed in the tables above. Theymay also be of other appropriate materials. The second sphere 504 andthe hole 502 and its terminus 503 should fit together closely withoutexcessive tolerance or gap.

A plug 505 preferably of the same substrate material as first sphere 501is formed or obtained. The plug 505 has a first end 505 a and a secondend 505 b and substrate material therebetween in order to fill the hole502 except for that portion of the hole 502 occup or raceied by thesecond sphere 504 adjacent the hole terminus 503. The plug 505preferably has a concave hemispherical receptacle 506 at its first end505 a so that plug 505 will closely abut second sphere 504 across abouthalf the spherical surface of second sphere 504. The plug 505 isgenerally cylindrical in shape. The substrate assembly including onesubstrate sphere placed inside of another may then be loaded withdiamond feedstock 507 and sintered under high pressure at hightemperature to form a spherical polycrystalline diamond compact.

Referring to FIG. 5B, another substrate geometry for manufacturingspherical polycrystalline diamond compacts of the invention is depicted.An inner core sphere 550 of appropriate substrate material is selected.Then an outer substrate first hemisphere 551 and outer substrate secondhemisphere 552 are selected. Each of the outer substrate first andsecond hemispheres 551 and 552 are formed so that they each have ahemispherical receptacle 551 a and 552 a shaped and sized to accommodateplacement of the hemispheres about the exterior of the inner core sphere550 and thereby enclose and encapsulate the inner core sphere 550. Thesubstrates materials of inner core sphere 550 and hemispheres 551 and552 are preferably selected form those listed in the tables above orother appropriate materials.

With the hemispheres and inner core sphere assembled, diamond feedstock553 may be loaded about the exterior of the hemispheres and hightemperature and high pressure sintering may proceed in order to form aspherical polycrystalline diamond compact.

Although FIGS. 5A and 5B depict two-layer substrates, it is possible touse multiple layer substrates (3 or more layers) for the manufacture ofpolycrystalline diamond compacts or polycrystalline cubic boron nitridecompacts. The selection of a substrate material, substrate geometry,substrate surface topographical features, and substrates having aplurality of layers (2 or more layers) of the same or differentmaterials depend at least in part on the thermo-mechanical properties ofthe substrate, the baro-mechanical properties of the substrate, and thebaro-mechanical properties of the substrate.

Referring to FIG. 5C, another substrate configuration for makinggenerally spherical polycrystalline diamond compacts is depicted. Thesubstrate 520 is in the general form of a sphere. The surface of thesphere includes substrate surface topography intended to enhancefixation of a diamond table to the substrate. The substrate has aplurality of depressions 521 formed on its surface. Each depression 521is formed as three different levels of depression 521 a, 521 b and 521c. The depressions are depicted as being concentric circles, each ofapproximately the same depth, but their depths could vary, the circlesneed not be concentric, and the shape of the depressions need not becircular. The depression walls 521 d, 521 e and 521 f are depicted asbeing parallel to a radial axis of the depressions which axis is normalto a tangent to the theoretical spherical extremity of the sphere, butcould have a different orientation if desired. As depicted, the surfaceof the substrate sphere 522 has no topographical features other than thedepressions already mentioned, but could have protrusions, depressionsor other modifications as desired. The width and depth dimensions of thedepressions 521 may be varied according to the polycrystalline diamondcompact that is being manufactured.

Diamond feedstock may be loaded against the exterior of the substratesphere 520 and the combination may be sintered at diamond stablepressures to produce a spherical polycrystalline diamond compact. Use ofsubstrate surface topographical features on a generally sphericalsubstrate provides a superior bond between the diamond table and thesubstrate as described above and permits a polycrystalline diamondcompact to be manufactured using a single layer substrate. That isbecause of the gripping action between the substrate and the diamondtable achieved by use of substrate surface topographical features.

Referring to FIG. 5D, a segmented spherical substrate 523 is depicted.The substrate has a plurality of surface depressions 524 equally spacedabout its exterior surface. These depressions as depicted are formed inlevels of three different depths. The first level 524 a is formed to apredetermined depth and is of pentagonal shape about its outerperiphery. The second level 524 b is round in shape and is formed to apredetermined depth which may be different from the predetermined depthof the pentagon. The third level 524 c is round in shape in is formed toa predetermined depth which may be different from each of the otherdepths mentioned above. Alternatively, the depressions may be formed toonly one depth, may all be pentagonal, or may be a mixture of shapes.The depressions may be formed by machining the substrate sphere.

Referring to FIG. 5E, a cross section of an alternative substrateconfiguration for making a polycrystalline diamond compact is shown. Apolycrystalline diamond compact 525 is shown. The compact 525 isspherical. The compact 525 includes a diamond table 526 sintered to asubstrate 527. The substrate is partially spherical in shape at itsdistal side 527 a and is dome-shaped on its proximal side 527 b.Alternatively, the proximal side 527 b of the substrate 527 may bedescribed as being partially spherical, but the sphere on which it isbased has a radius of smaller dimension than the radius of the sphere onwhich the distal side 527 a of the substrate is based. Each of the top527 c and bottom 527 d are formed in a shape convenient to transitionfrom the proximal side 527 b substrate partial sphere to the distal side527 a substrate partial sphere. This substrate configuration hasadvantages in that it leaves a portion of substrate exposed for drillingand attaching fixation components without disturbing residual stressfields of the polycrystalline diamond table. It also provides a portionof the substrate that does not have diamond sintered to it, allowingdilatation of the substrate during sintering without disruption of thediamond table. More than 180 degrees of the exterior of the substratesphere has diamond on it, however, so the part is useful as a head orother articulation surface.

Referring to FIG. 5F, a cross section of an alternative substrateconfiguration for making a polycrystalline diamond compact is shown. Apolycrystalline diamond compact 528 is depicted having a diamond table529 and a substrate 530. The substrate has topographical features 531for enhancing strength of the diamond to substrate interface. Thetopographical features may include rectangular protrusions 532 spacedapart by depressions 533 or corridors. The distal side of the substrateis formed based on a sphere of radius r. The proximal side of thesubstrate 530 b is formed based on a sphere of radius r′, where r>r′.Usually the surface modifications will be found beneath substantiallyall of the diamond table.

Referring to FIG. 5G, a head 535 of a bearing component is depicted. Thehead 535 that includes a diamond table 536 sintered to a substrate 536.The substrate is configured as a sphere with a protruding cylindricalshape. The head 535 is formed so that a quantity of substrate protrudesfrom the spherical shape of the head to form a neck 538 and attachment537 which may be attached to an appropriate body by any known attachmentmethod, such as by self-locking taper fit, welding, threads or otherattachment mechanisms. The use of a neck 538 preformed on the substratethat is used to manufacture a polycrystalline diamond compact 535provides an attachment point on the polycrystalline diamond compact thatmay be utilized without disturbing the residual stress field of thecompact.

Any of the previously mentioned substrate configurations and substratetopographies and variations and derivatives of them may be used tomanufacture a polycrystalline diamond compact for use in a load bearingor articulation surface environment.

In various embodiments of the invention, a single layer substrate may beutilized. In other embodiments of the invention, a two-layer substratemay be utilized, as discussed. Depending on the properties of thecomponents being used, however, it may be desired to utilize a substratethat includes three, four or more layers. Such multi-layer substratesare intended to be comprehended within the scope of the invention.

The preferred substrate geometry for manufacturing an cup or race orother concave spherical, hemispherical or partially sphericalpolycrystalline diamond compact of the invention differs from that usedto manufacture a convex spherical polycrystalline diamond compact.Referring to FIGS. 6A-1, 6A-2, 6B-1 and 6B-2-6C below, the preferredassembly for manufacturing a concave spherical polycrystalline diamondcompact (such as that used in an cup or race) are depicted. Thesubstrate 601 (and 601 a and 601 b) is preferably in the form of acylinder with a hemispherical receptacle 602 (and 602 a and 602 b)formed into one of its ends.

Two substrate cylinders 601 a and 601 b are placed so that theirhemispherical receptacles 602 a and 602 b are adjacent each other, thusforming a spherical cavity 604 between them. A sphere 603 of anappropriate substrate material is located in the cavity 604. Diamondfeedstock 605 is located in the cavity 604 between the exterior of thesphere 603 and the concave surfaces of the receptacles 602 a and 602 bof the substrate cylinders 601 a and 601 b. The assembly is placed intoa refractory metal can 610 for sintering. The can has a first cylinder610 a and a second cylinder 601 b. The two cylinders join at a lip 611.

After such an assembly is sintered, the assembly may be slit, cut orground along the center line 606 in order to form a first cup or raceassembly 607 a and a second cup or race assembly 607 b. The preferredsubstrate materials for the cylinders 602 a and 602 b are CoCrMo (ASTMF-799) and CoCrW (ASTM F-90), and the preferred substrate material forthe sphere 603 is preferably CoCrMo (ASTM F-799), although anyappropriate substrate material may be used, including some of thoselisted in the tables.

While two layer substrates have been discussed above for manufacturingconcave and convex spherical polycrystalline diamond compacts, it isalso possible to use substrates consisting of more than two layers ofmaterial or substrates of a single type of material in manufacturingspherical polycrystalline diamond compacts.

2. Substrate Surface Topography

Depending on the application, it may be advantageous to includesubstrate surface topographical features on a substrate that is to beformed into a polycrystalline diamond compact. Regardless whether aone-piece, a two-piece of a multi-piece substrate is used, it may bedesirable to modify the surface of the substrate or providetopographical features on the substrate in order to increase the totalsurface area of diamond to enhance substrate to diamond contact and toprovide a mechanical grip of the diamond table.

The placement of topographical features on a substrate serves to modifythe substrate surface geometry or contours from what the substratesurface geometry or contours would be if formed as a simple planar ornon-planar figure. Substrate surface topographical features may includeone or more different types of topographical features which result inprotruding, indented or contoured features that serve to increasesurface, mechanically interlock the diamond table to the substrate,prevent crack formation, or prevent crack propagation.

Substrate surface topographical features or substrate surfacemodifications serve a variety of useful functions. Use of substratetopographical features increases total substrate surface area of contactbetween the substrate and the diamond table. This increased surface areaof contact between diamond table and substrate results in a greatertotal number of chemical bonds between diamond table and substrate thanif the substrate surface topographical features were absent, thusachieving a stronger polycrystalline diamond compact.

Substrate surface topographical features also serve to create amechanical interlock between the substrate and the diamond table. Themechanical interlock is achieved by the nature of the substratetopographical features and also enhances strength of the polycrystallinediamond compact.

Substrate surface topographical features may also be used to distributethe residual stress field of the polycrystalline diamond compact over alarger surface area and over a larger volume of diamond and substratematerial. This greater distribution can be used to keep stresses belowthe threshold for crack initiation and/or crack propagation at thediamond table/substrate interface, within the diamond itself and withinthe substrate itself.

Substrate surface topographical features increase the depth of thegradient interface or transition zone between diamond table andsubstrate, in order to distribute the residual stress field through alonger segment of the composite compact structure and to achieve astronger part.

Substrate surface modifications can be used to created a sinteredpolycrystalline diamond compact that has residual stresses that fortifythe strength of the diamond layer and yield a more robustpolycrystalline diamond compact with greater resistance to breakage thanif no surface topographical features were used. This is because in orderto break the diamond layer, it is necessary to first overcome theresidual stresses in the part and then overcome the strength of thediamond table.

Substrate surface topographical features redistribute forces received bythe diamond table. Substrate surface topographical features cause aforce transmitted through the diamond layer to be re-transmitted fromsingle force vector along multiple force vectors. This redistribution offorces travelling to the substrate avoids conditions that would deformthe substrate material at a more rapid rate than the diamond table, assuch differences in deformation can cause cracking and failure of thediamond table.

Substrate surface topographical features may be used to mitigate theintensity of the stress field between the diamond and the substrate inorder to achieve a stronger part.

Substrate surface topographical features may be used to distribute theresidual stress field throughout the polycrystalline diamond compactstructure in order to reduce the stress per unit volume of structure.

Substrate surface topographical features may be used to mechanicallyinterlock the diamond table to the substrate by causing the substrate tocompress over an edge of the diamond table during manufacturing.Dovetailed, hemispherical and lentate modifications act to provide forcevectors that tend to compress and enhance the interface of diamond tableand substrate during cooling as the substrate dilitates radially.

Substrate surface topographical features may also be used to achieve amanufacturable form. As mentioned herein, differences in coefficient ofthermal expansion and modulus between diamond and the chosen substratemay result in failure of the polycrystalline diamond compact duringmanufacturing. For certain parts, the stronger interface betweensubstrate and diamond table that may be achieved when substratetopographical features are used can achieve a polycrystalline diamondcompact that can be successfully manufactured. But if a similar part ofthe same dimensions is to be made using a substrate with a simplesubstrate surface rather than specialized substrate surfacetopographical features, the diamond table may crack or separate from thesubstrate due to differences in coefficient of thermal expansion ormodulus of the diamond and the substrate.

Examples of useful substrate surface topographical features includewaves, grooves, ridges, other longitudinal surface features (any ofwhich may be arranged longitudinally, lattitudinally, crossing eachother at a desired angle, in random patterns, and in geometricpatterns), three dimensional textures, spherical segment depressions,spherical segment protrusions, triangular depressions, triangularprotrusions, arcuate depressions, arcuate protrusions, partiallyspherical depressions, partially spherical protrusions, cylindricaldepressions, cylindrical protrusions, rectangular depressions,rectangular protrusions, depressions of n-sided polygonal shapes where nis an integer, protrusions of n-sided polygonal shapes, a waffle patternof ridges, a waffle iron pattern of protruding structures, dimples,nipples, protrusions, ribs, fenestrations, grooves, troughs or ridgesthat have a cross-sectional shape that is rounded, triangular, arcuate,square, polygonal, curved, or otherwise, or other shapes. Machining,pressing, extrusion, punching, injection molding and other manufacturingtechniques for creating such forms may be used to achieve desiredsubstrate topography. Although for illustration purposes, some sharpcorners are depicted on substrate topography or other structures in thedrawings, in practice it is expected that all corners will have a smallradius to achieve a component with superior durability.

FIGS. 3A-3U depict a few possible substrate surface modifications.Referring to FIG. 3A, a ball structure on a stem is depicted thatfeatures concave and convex substrate surface topographical features. Ahead 380 is shown that has a diamond table 382 sintered to a substrate383. The substrate 383 has surface topography that includes concavearcuate grooves 384 and convex arcuate ridges 385 radiating from a pointon the substrate. The diamond 382 covers the substrate topographicalfeatures, resulting in a greater surface area of contact between thediamond table and the substrate than if a simple rounded substrate wereemployed.

FIG. 3B shows redistribution of a force applied to the head 380 of FIG.3A. When a force F1 is applied to the head 380, that force F1 isredistributed along force vectors F2 and F3, as shown. Thus, although onthe diamond table 382 a single force vector is received, that forcevector is broken down into smaller forces and transmitted through thesubstrate 383. This redistribution of forces decreases the possibilityof a differential in rates of deformation of the diamond table and thesubstrate and therefore reduces the chance of the diamond table crackingand failing.

FIG. 3C depicts use of substrate topographical features on a head in aball and cup or race bearing assembly. The cup or race 386 is mounted ina desired structure 387. The cup or race 386 has a polycrystallinediamond table 388 attached to a substrate 389. The head 390 includes atable of polycrystalline diamond 391 on a substrate 392.

The substrate 392 has surface topography including grooves 393 orientedso that they will be generally vertical when the bearing component is inuse. The primary force vector F1 is generally parallel to the grooves393. The force zone 394 due to use is shown above the cup or race. Useof substrate surface topography that includes grooves that are generallyvertically oriented when the bearing is in use achieves widerredistribution of forces.

FIG. 3D depicts a convex sphere 350 of appropriate substrate material.The sphere 350 has a polar axis 351 and an equator 352. A plurality ofsurface modifications 353 were formed in the surface of the sphere 350.The surface modifications are arranged in a close offset configuration.The surface modifications can range from less than about 0.001 inch tomore than about 0.750 inch diameter cylindrical depressions having adepth of from less than about 0.001 inch to more than about 0.750 inchor otherwise as desired. Very small surface topographical features canbe created by use of a laser. In most embodiments of the invention,substrate surface topographical features will cover from about 1% toabout 99% of the surface of the substrate beneath the diamond table. Thesubstrate surface topographical features will have a depth of from about1% of the radius of the part to about 50% of the radius of the part.Discrete substrate surface topographical features will have a dimensionmeasured along a tangent to the substrate surface of from about 1% toabout 50% of the radius of the part.

FIG. 3E depicts a cross section of a polycrystalline diamond compactformed using a spherical substrate with a modified substrate surface,such as that depicted in FIG. 3A. The compact 360 has a diamond layer361 sintered to a substrate 362. The substrate 362 has surfacemodifications 363 in which diamond 361 is found. The substrate in thevicinity of the surface modification 363 tends to grip the diamond atforce lines F1 and F2, thus adding a mechanical gripping advantage tothe chemical bonds of the polycrystalline diamond compact, and resultingin a very strong part.

FIG. 3F depicts substrate surface convex rounded protrusions 379 ornipples on a substrate 378. The nipples or protrusions are depicted asbeing rounded or arcuate. FIG. 3G depicts substrate surface protrudingridges 377 and grooves 376 on a substrate 375. FIG. 3H depicts asubstrate 374 having elevated ridges 273 and rounded or arcuate grooves372 between the ridges. This substrate surface configuration may be madeby machining grooves that are round in cross section in a sphericalsubstrate. The ridges 377 are substrate material left between thegrooves that have been machined.

FIG. 3I depicts a convex spherical substrate 320. Absent specializedsubstrate surface topographical features, the substrate 320 would be inthe form of a simple sphere as depicted by circle 323. This substrate320 includes rounded or arcuate wavelike forms on its exterior surfacethat take the shape of protruding ridges 322 and depressed grooves 321.

FIG. 3J depicts a convex spherical substrate 324. The substrate 324includes protruding rectangular forms 325 which form a waffle-likepattern on the surface of the substrate 324. Between each protrudingform 325 is a gap, groove, trough, or alley 326.

FIG. 3K depicts a substrate 327. Such a substrate may have been simpleconvex spherical as indicated by dashed circle 328, but has beenmachined to have its present form. The substrate 327 has had polygonalshapes 329 formed into its surface to create specialized topographicalfeatures for an interface with a diamond table.

FIG. 3L depicts a generally spherical substrate 330 having a pluralityof depressions 331 formed in its surface. The surface 334 of thesubstrate sphere 330 is spherical in shape except for the depressions331. The depressions have a circular upper rim 335, a circular bottom332, and a sidewall 333 of a desired depth. As desired, the maximumdiameter of the rim 335 of a depression may have the same or greaterdimension than the maximum diameter of the bottom 332 of the samedepression. If the two diameters are the same, then the depression willhave a cylindrical shape. If the rim 335 has a greater diameter than thebottom 333, then the depression will have a frusto-conical shape.Diamond may be bonded on a substrate as depicted in FIG. 3L in tablethat has a thickness that completely covers the outside surface of thesubstrate. In that case, the diamond table will be thicker in areasabove a depression than in other areas. If such a diamond table is used,then from outward appearance, the substrate surface topographicalfeatures will not be discernible. Alternatively, diamond may be bondedin the depressions only, leaving the substrate between depressionsexposed. Such a configuration is discussed in more detail with respectto FIG. 3Q.

FIG. 3M depicts a generally spherical substrate 336 having a pluralityof protrusions 337 on its surface. The surface 338 of the substratesphere 336 is spherical in shape except for the protrusions 337. Theprotrusions have a circular lower rim 339, a circular upper rim 340, anda sidewall 341 of a desired height. The protrusion tops 342 may be ofany desired shape, such as flat, domed, partially spherical, arcuate, orotherwise. As desired, the maximum diameter of the lower rim 339 and theupper rim 340 may differ. If the two diameters are the same and thesidewall 341 is straight, then the protrusion will have a generallycylindrical shape. If the rim 339 has a greater diameter than the rim340, then the protrusion will have a generally frusto-conical shape. Adiamond table may be attached to the substrate of FIG. 3M to that thediamond table completely covers the substrate surface modifications andthe areas between them. In such a configuration, from outward appearancethe substrate surface modifications would not be discernible.Alternatively, diamond may be attached to the substrate only between thesubstrate surface modifications, creating a web or network of exposeddiamond having discontinuous areas of exposed substrate material.

FIG. 3N depicts a spherical polycrystalline diamond compact 342including a diamond table 343 and a substrate 344. The substrate 344includes topographical surface modifications. The surface modificationsinclude dovetail depressions 345 formed in the substrate.Polycrystalline diamond has formed in the dovetail to create a tightmechanical interlock between the diamond table and the substrate. Thisstructure may be achieved by forming depressions in the surface of asubstrate that do not have a dovetail shape. During sintering, thedovetail interlock between the substrate and the diamond table can beformed due to differences in the coefficient of thermal expansion andmodulus between diamond and the substrate material.

FIG. 3O depicts a partially spherical polycrystalline diamond compact3343 having a diamond table 346 and a substrate 347. The diamond table346 presents a continuous diamond load bearing and articulation surface.The substrate 347 has been formed with surface topography intended toeffect a stronger bond with the diamond table. The substrate 347includes hemispherical or lentate modifications 348 formed on thesubstrate outer surface. The modifications depicted are concavepartially spherical depressions on the substrate surface.Polycrystalline diamond forms in the depressions 349. During sintering,as the polycrystalline diamond compact cools, the substrate tends todilatate radially. The hemispherical depressions of this surfacemodification provide force vectors that compress and enhance theinterface between the diamond table and the substrate, to achieve a muchstronger bond between the diamond table and the substrate. Thus, amechanical grip or interlock is created between the diamond table andthe substrate both as a result of the differences in CTE between thediamond and the substrate and as a result of the substrate topographicalfeatures.

FIG. 3P depicts a partially spherical polycrystalline diamond compact3320. The compact 3320 includes a diamond table 3321 and a substrate3322. The substrate 3322 has topographical features that include ridges3323 and troughs 3324 that are triangular in cross section. The use ofsubstrate topographical features such as these provides a gradientinterface or transition zone between the diamond and the substrate asdescribed elsewhere herein. The gradient interface I found in apolycrystalline diamond compact that has substrate topographicalfeatures is typically of greater depth than that found in apolycrystalline diamond compact that has a substrate with a simplesurface. Consequently, the residual stress field in a polycrystallinediamond compact that has substrate topographical features is distributedthrough a longer segment of the composite compact structure, and isdistributed over a greater volume of diamond and substrate materials.The result is a polycrystalline diamond compact that is stronger andmore stable than that which may be achieved without the use of substratetopographical features.

FIG. 3Q depicts a partially spherical polycrystalline diamond compact.The compact includes a substrate 390 formed with diamond receptacles,depressions or indentations 351. On sintering, polycrystalline diamond349 is formed in the depressions 351 in order to create a load bearingand articulation surface that includes discontinuous or segmented areasof diamond. Between the diamond areas 349, there is exposed substratematerial 350 on the load bearing and articulation surface. During finishpolishing, the lesser hardness of the substrate material compared todiamond will tend to cause the exposed substrate 350 to be relieved,presenting a load bearing and articulation surface on which the primarycontact and articulation is provided by the diamond patches 349. Ifdesired, the exposed substrate 350 may be machined or polished toprovide sufficient relief to serve as a channel for communicatinglubricating fluids to the load bearing and articulation surface.

FIG. 3R depicts a spherical ball 352 that has a substrate 353 and adiamond table 354. The substrate 353 includes a receptacle 355 forreceiving an attachment mechanism. The diamond table 354 covers lessthan the entire surface of the substrate 353. As depicted, the diamondtable 354 has a hemispherical configuration. The substrate 353 has beenprepared with an annular groove or ring 356 about its equator. Thediamond table 354 is thicker in the area of the annular groove 356 andoccup or raceies the annular groove 356 in order to provide strongbonding at the edge of the diamond table 354.

FIG. 3S depicts a cup or race 357 having a substrate 358 and a diamondtable load bearing and articulation surface 359. The substrate 358includes a lip 360 which interlocks the diamond table 359 in place inthe cup or race 357. Although the lip 360 structure may be formed in thesubstrate 358 prior to sintering of the polycrystalline diamond compact,the lip 360 structure may also be formed or enhanced by dilatation ofthe substrate material during sintering. The lip reduces or eliminatesedge effect at the extreme radial interface of the diamond table 359 andthe substrate 358 in order to provide a stronger and more durablecomponent.

FIG. 3T depicts a generally spherical substrate 362 having a pluralityof truncated pyramid-like or polygonal protrusions 363 on its surface.The surface 364 of the substrate sphere 362 is generally spherical inshape except for the protrusions 363. The protrusions have a square orrectangular lower perimeter 365, a square or rectangular upper perimeter366 and a side wall 364 of desired height. The protrusion tops 366 maydiffer to form a plurality of different angles between the lower andupper perimeters. If the two perimeters are the same dimension and thesidewall 367 is straight, then the protrusions will have a generallysquare or rectangular shape. If the upper perimeter 366 has a smallerdimension than the lower perimeter, then the protrusion will have agenerally truncated pyramid shape. If the upper perimeter 366 is largerthan the lower perimeter 365, the protrusion will have a generallyinverted truncated pyramid shape. A diamond table may attach to thesubstrate of FIG. 3T so that the diamond table completely covers thesubstrate surface modifications and the areas between them. In such aconfiguration, from outward appearance, the substrate surfacemodifications would not be discernable. Alternatively, diamond may beattached to the substrate only between the substrate surfacemodifications, creating a web or network of exposed diamond havingdiscontinuous areas of exposed substrate material.

FIG. 3U depicts a generally spherical substrate 368 having a pluralityof depressions 369 formed into its surface. The surface 370 of thesubstrate sphere 368 is spherical in shape except for the depressions369. The depressions have a square or rectangular upper perimeter 371, asquare or rectangular bottom 372, and a sidewall 373 of a desired depth.As desired, the maximum upper perimeter 371 of a depression may have thesame dimension of the bottom perimeter 372 of the same depression. Ifthe perimeters are the same, then the depression will have a rectangularsquare shape. If the upper perimeter 371 has a greater dimension thanthe bottom perimeter 352, then the depression will have an invertedtruncated pyramid shape. Diamond may be bonded on a substrate asdepicted in FIG. 3U in a table that has a thickness that completelycovers the outside surface of the substrate. In that case the diamondtable will be thicker in areas above a depression than in other areas.If such a diamond table is used, then from outward appearance, thesubstrate surface topographical features will not be discernible.Alternatively, diamond may be bonded in the depressions only, leavingthe substrate between depressions exposed.

Although many substrate topographies have been depicted in convexspherical substrates, those surface topographies may be applied toconvex spherical substrate surfaces, other non-planar substratesurfaces, and flat substrate surfaces. Substrate surface topographieswhich are variations or modifications of those shown, and othersubstrate topographies which increase component strength or durabilitymay also be used.

Diamond Feedstock Selection

It is anticipated that typically the diamond particles used will be inthe range of less than 1 micron to more than 100 microns. In someembodiments of the invention, however, diamond particles as small as 1nanometer may be used. Smaller diamond particles are preferred forsmoother bearing surfaces. Commonly, diamond particle sizes will be inthe range of 0.5 to 2.0 microns or 0.1 to 10 microns. It is preferredthat the diamond particles will be roughly spherical in some embodimentsof the invention. The diamond feedstock may include the addition ofvarious metals as desired and as discussed elsewhere, such as SiC, SiN₂,TiN, TB₂ and others. A preferred diamond feedstock is shown in the tablebelow.

TABLE 3 EXAMPLE BIMODAL DIAMOND FEEDSTOCK MATERIAL AMOUNT 4 to 8 microndiamond about 90% 0.5 to 1.0 micron diamond about 9% Titaniumcarbonitride powder about 1%

This formulation mixes some smaller and some larger diamond crystals sothat during sintering, the small crystals may dissolve and thenrecrystallize in order to form a lattice structure with the largerdiamond crystals. Titanium carbonitride powder may optionally beincluded in the diamond feedstock in order to prevent excessive diamondgrain growth during sintering in order to produce a finished productthat has smaller diamond crystals.

Another diamond feedstock example is provided in the table below.

TABLE 4 EXAMPLE TRIIMODAL DIAMOND FEEDSTOCK MATERIAL AMOUNT Size xdiamond crystals about 90% Size 0.1x diamond crystals about 9% Size0.01x diamond crystals about 1%

The trimodal diamond feedstock described above can be used with anysuitable diamond feedstock having a first size or diameter “x”, a secondsize 0.1× and a third size 0.01×. This ratio of diamond crystals allowspacking of the feedstock to about 89% theoretical density, closing mostinterstitial spaces and providing the densest diamond table in thefinished polycrystalline diamond compact.

Another diamond feedstock example is provided in the table below.

TABLE 5 EXAMPLE TRIIMODAL DIAMOND FEEDSTOCK MATERIAL AMOUNT Size xdiamond crystals about 88-92% Size 0.1x diamond crystals about 8-12%Size 0.01x diamond crystals about 0.8-1.2%

Another diamond feedstock example is provided in the table below.

TABLE 6 EXAMPLE TRIIMODAL DIAMOND FEEDSTOCK MATERIAL AMOUNT Size xdiamond crystals about 85-95% Size 0.1x diamond crystals about 5-15%Size 0.01x diamond crystals about 0.5-1.5%

Another diamond feedstock example is provided in the table below.

TABLE 7 EXAMPLE TRIIMODAL DIAMOND FEEDSTOCK MATERIAL AMOUNT Size xdiamond crystals about 80-90% Size 0.1x diamond crystals about 10-20%Size 0.01x diamond crystals about 0-2%

In some embodiments of the invention, the diamond feedstock used will bediamond powder having a greatest dimension of about 100 nanometers orless. In some embodiments of the invention it is preferred to includesome solvent-catalyst metal with the diamond feedstock to aid in thesintering process, although in many applications there will be asignificant solvent-catalyst metal sweep from the substrate duringsintering as well.

Solvent Metal Selection

It has already been mentioned that solvent metal will sweep from thesubstrate through the diamond feedstock during sintering in order tosolvate some diamond crystals so that they may later recrystallize andform a diamond-diamond bonded lattice network that characterizespolycrystalline diamond. It is preferred, however, to include somesolvent-catalyst metal in the diamond feedstock only when required tosupplement the sweep of solvent-catalyst metal from the substrate.

Traditionally, cobalt, nickel and iron have been used as solvent metalsfor making polycrystalline diamond. In bearing components, however, thesolvent metal must be biocompatible. The inventors prefer use of asolvent metal such as CoCrMo or CoCrW. Platinum and other materialscould also be used for a binder.

It is important not just to add the solvent metal to diamond feedstock,but also to include solvent metal in an appropriate proportion and tomix it evenly with the feedstock. The inventors prefer the use of about86% diamond feedstock and 15% solvent metal by mass (weight), butanticipate that useful ratios of diamond feedstock to solvent metal willinclude 5:95, 10:90, 20:80, 30:70, 40:60, 50:50, 60:40, 65:35, 75:25,80:20, 90:10, 95:5, 97:3, 98:2, 99:1, 99.5:0.5, 99.7:0.3, 99.8:0.2,99.9:0.1 and others.

In order to mix the diamond feedstock with solvent-catalyst metal, firstthe amounts of feedstock and solvent metal to be mixed may be placedtogether in a mixing bowl, such as a mixing bowl made of the desiredsolvent-catalyst metal. Then the combination of feedstock and solventmetal may be mixed at an appropriate speed (such as 200 rpm) with drymethanol and attritor balls for an appropriate time period, such as 30minutes. The attritor balls, the mixing fixture and the mixing bowl arepreferably made from the solvent-catalyst metal. The methanol may thenbe decanted and the diamond feedstock separated from the attritor balls.The feedstock may then be dried and cleaned by firing in a molecularhydrogen furnace at about 1000 degrees Celsius for about 1 hour. Thefeedstock is then ready for loading and sintering. Alternatively, it maybe stored in conditions which will preserve its cleanliness. Appropriatefurnaces which may be used for firing also include hydrogen plasmafurnaces and vacuum furnaces.

Loading Diamond Feedstock

The loading technique for diamond feedstock used is critical to thesuccess of the final product. As mentioned previously, the diamondfeedstock must be loaded to uniform density in order to produce acomponent that lacks unwanted distortion.

Referring to FIG. 7, an apparatus for carrying out a preferred loadingtechnique is depicted. The apparatus includes a spinning rod 701 with alongitudinal axis 702, the spinning rod being capable of spinning aboutits longitudinal axis. The spinning rod 701 has an end 703 matched tothe size and shape of the part to be manufactured. For example, if thepart to be manufactured is a head or an cup or race, the spinning rodend 703 should be hemispherical.

A compression ring 704 is provided with a bore 705 through which thespinning rod 701 may project. A die 706 or can is provided with a cavity707 also matched to the size and shape of the part to be made.

In order to load diamond feedstock, the spinning rod is placed into adrill chuck and the spinning rod is aligned with the center point of thedie. The depth to which the spinning rod stops in relation to the cavityof the die is controlled with a set screw and monitored with a dialindicator.

The die is charged with a known amount of diamond feedstock material.The spinning rod is then spun about its longitudinal axis and loweredinto the die cavity to a predetermined depth. The spinning rod contactsand rearranges the diamond feedstock during this operation. Then thespinning of the spinning rod is stopped and the spinning rod is lockedin place.

The compression ring is then lowered around the outside of the spinningrod to a point where the compression ring contacts diamond feedstock inthe cavity of the die. The part of the compression ring that contactsthe diamond is annular. The compression ring is tamped up and down tocompact the diamond. This type of compaction is used to distributediamond material throughout the cavity to the same density and may bedone in stages to prevent bridging. Packing the diamond with thecompaction ring causes the density of the diamond around the equator ofthe sample caused to be very uniform and the same as that of the polarregion in the cavity. In this configuration, the diamond sinters in atruly spherical fashion and the resulting part maintains its sphericityto close tolerances.

Another method which may be employed to maintain a uniform density ofthe feedstock diamond is the use of a binder. A binder is added to thecorrect volume of feedstock diamond, and then the combination is pressedinto a can. Some binders which might be used include polyvinyl butyryl,polymethyl methacrylate, polyvinyl formol, polyvinyl chloride acetate,polyethylene, ethyl cellulose, methylabietate, paraffin wax,polypropylene carbonate and polyethyl methacrylate.

In a preferred embodiment of the invention, the process of bindingdiamond feedstock includes four steps. First, a binder solution isprepared. A binder solution may be prepared by adding about 5 to 25%plasticizer to pellets of poly(propylene carbonate), and dissolving thismixture in solvent such as 2-butanone to make about a 20% solution byweight.

Plasticizers that may be used include nonaqueous binders generally,glycol, dibutyl phthalate, benzyl butyl phthalate, alkyl benzylphthalate, diethylhexyl phthalate, diisoecyl phthalate, diisononylphthalate, dimethyl phthalate, dipropylene glycol dibenzoate, mixedglycols dibenzoate, 2-ethylhexyl diphenyl dibenzoate, mixed glycolsdibenzoate, 2-ethylhexyl diphenyl phosphate, isodecyl diphenylphosphate, isodecyl diphenl phosphate, tricrestyl phosphate, tributoxyethyl phosphate, dihexyl adipate, triisooctyl trimellitate, dioctylphthalate, epoxidized linseed oil, epoxidized soybean oil, acetyltriethyl citrate, propylene carbonate, various phthalate esters, butylstearate, glycerin, polyalkyl glycol derivatives, diethyl oxalate,paraffin wax and triethylene glycol. Other appropriate plasticizers maybe used as well.

Solvents that may be used include 2-butanone, methylene chloride,chloroform, 1,2-dichloroethne, trichlorethylene, methyl acetate, ethylacetate, vinyl acetate, propylene carbonate, n-propyl acetate,acetonitrile, dimethylformamide, propionitrile, n-methyl-2-pyrrolidene,glacial acetic acid, dimethyl sulfoxide, acetone, methyl ethyl ketone,cyclohexanone, oxysolve 80a, caprotactone, butyrolactone,tetrahydrofuran, 1,4 dioxane, propylene oxide, cellosolve acetate,2-methoxy ethyl ether, benzene, styrene, xylene, ethanol, methanol,toluene, cyclohexane, chlorinated hydrocarbons, esters, ketones, ethers,ethyl benzene and various hydrocarbons. Other appropriate solvents maybe used as well.

Second, diamond is mixed with the binder solution. Diamond may be addedto the binder solution to achieve about a 2-25% binder solution (thepercentage is calculated without regard to the 2-butanone).

Third, the mixture of diamond and binder solution is dried. This may beaccomplished by placing the diamond and binder solution mixture in avacuum oven for about 24 hours at about 50 degrees Celsius in order todrive out all of the solvent 2-butanone. Fourth, the diamond and bindermay be pressed into shape. When the diamond and binder is removed fromthe oven, it will be in a clump that may be broken into pieces which arethen pressed into the desired shape with a compaction press. A pressingspindle of the desired geometry may be contacted with the bound diamondto form it into a desired shape. When the diamond and binder have beenpressed, the spindle is retracted. The preferred final density ofdiamond and binder after pressing is at least about 2.6 grams per cubiccentimeter.

If a volatile binder is used, it should be removed from the shapeddiamond prior to sintering. The shaped diamond is placed into a furnaceand the binding agent is either gasified or pyrolized for a sufficientlength of time such that there is no binder remaining. Polycrystallinediamond compact quality is reduced by foreign contamination of thediamond or substrate, and great care must be taken to ensure thatcontaminants and binder are removed during the furnace cycle. Ramp upand the time and temperature combination are critical for effectivepyrolization of the binder. For the binder example given above, thedebinding process preferably used to remove the binder is as follows.Reviewing FIG. 7A while reading this description may be helpful.

First, the shaped diamond and binder are heated to from ambienttemperature to about 500 degrees Celsius. The temperature is preferablyincreased by about 2 degrees Celsius per minute until about 500 degreesCelsius is reached. Second, the temperature of the bound and shapeddiamond is maintained at about 500 degrees Celsius for about 2 hours.Third, the temperature of the diamond is increased again. Thetemperature is preferably increased from about 500 degrees Celsius byabout 4 degrees per minute until a temperature of about 950 degreesCelsius is reached. Fourth, the diamond is maintained at about 950degrees Celsius for about 6 hours. Fifth, the diamond is then permittedto return to ambient temperature at a temperature decrease of about 2degrees per minute.

In some embodiments of the invention, it may be desirable to preformbound diamond feedstock by an appropriate process, such as injectionmolding. The diamond feedstock may include diamond crystals of one ormore sizes, solvent-catalyst metal, and other ingredients to controldiamond recrystallization and solvent-catalyst metal distribution.Handling the diamond feedstock is not difficult when the desired finalcurvature of the part is flat, convex dome or conical. However, when thedesired final curvature of the part has complex contours, such asillustrated herein, providing uniform thickness and accuracy of contoursof the polycrystalline diamond compact is more difficult when usingpowder diamond feedstock. In such cases it may be desirable to performthe diamond feedstock before sintering.

If it is desired to perform diamond feedstock prior to loading into acan for sintering, rather than placing powder diamond feedstock into thecan, the steps described herein and variations of them may be followed.First, as already described, a suitable binder is added to the diamondfeedstock. Optionally, powdered solvent-catalyst metal and othercomponents may be added to the feedstock as well. The binder willtypically be a polymer chosen for certain characteristics, such asmelting point, solubility in various solvents, and CTE. One or morepolymers may be included in the binder. The binder may also include anelastomer and/or solvents as desired in order to achieve desiredbinding, fluid flow and injection molding characteristics. The workingvolume of the binder to be added to a feedstock preferably will be equalto or slightly more than the measured volume of empty space in aquantity of lightly compressed powder. Since binders typically consistof materials such as organic polymers with relatively high CTE's, theworking volume should be calculated for the injection moldingtemperatures expected. The binder and feedstock should be mixedthoroughly to assure uniformity of composition. When heated, the binderand feedstock will have sufficient fluid character to flow in highpressure injection molding. The heated feedstock and binder mixture isthen injected under pressure into molds of desired shape. The moldedpart then cools in the mold until set, and the mold can then be openedand the part removed. Depending on the final polycrystalline diamondcompact geometry desired, one or more molded diamond feedstock componentcan be created and placed into a can for polycrystalline diamond compactsintering. Further, use of this method permits diamond feedstock to bemolded into a desired form and then stored for long periods of timeprior to use in the sintering process, thereby simplifying manufacturingand resulting in more efficient production.

As desired, the binder may be removed from the injection molded diamondfeedstock form. A variety of methods are available to achieve this. Forexample, by simple vacuum or hydrogen furnace treatment, the binder maybe removed from the diamond feedstock form. In such a method, the formwould be brought up to a desired temperature in a vacuum or in a verylow pressure hydrogen (reducing) environment. The binder will thenvolatilize with increasing temperature and will be removed from theform. The form may then be removed from the furnace. When hydrogen isused, it helps to maintain extremely clean and chemically activesurfaces on the diamond crystals of the diamond feedstock form.

An alternative method for removing the binder from the form involvesutilizing two or polymer (such as polyethylene) binders with differentmolecular weights. After initial injection molding, the diamondfeedstock form is placed in a solvent bath which removes the lowermolecular weight polymer, leaving the higher molecular weight polymer tomaintain the shape of the diamond feedstock form. Then the diamondfeedstock form is placed in a furnace for vacuum or very low pressurehydrogen treatment for removal of the higher molecular weight polymer.

Partial or complete binder removal from the diamond feedstock form maybe performed prior to assembly of the form in a pressure assembly forpolycrystalline diamond compact sintering. Alternatively, the pressureassembly including the diamond feedstock form may be placed into afurnace for vacuum or very low pressure hydrogen furnace treatment andbinder removal.

Diamond feedstock may be selected and loaded in order to createdifferent types of gradients in the diamond table. These include aninterface gradient diamond table, an incremental gradient diamond table,and a continuous gradient diamond table.

If a single type or mix of diamond feedstock is loaded adjacent asubstrate, as discussed elsewhere herein, sweep of solvent-catalystmetal through the diamond will create an interface gradient in thegradient transition zone of the diamond table.

An incremental gradient diamond table may be created by loading diamondfeedstocks of differing characteristics (diamond particle size, diamondparticle distribution, metal content, etc.) in different strata orlayers before sintering. For example, a substrate is selected, and afirst diamond feedstock containing 60% solvent-catalyst metal by weightis loaded in a first strata adjacent the substrate. Then a seconddiamond feedstock containing 40% solvent-catalyst metal by weight isloaded in a second strata adjacent the first strata. Optionally,additional strata of diamond feedstock may be used. For example, a thirdstrata of diamond feedstock containing 20% solvent-catalyst metal byweight may be loaded adjacent the second strata.

A continuous gradient diamond table may be created by loading diamondfeedstock in a manner that one or more of its characteristicscontinuously vary from one depth in the diamond table to another. Forexample, diamond particle size may vary from large near a substrate (inorder to create large interstitial spaces in the diamond forsolvent-catalyst metal to sweep into) to small near the diamond bearingsurface in order to create a part that is strongly bonded to thesubstrate but that has a very low friction bearing surface.

The diamond feedstocks of the different strata may be of the same ordifferent diamond particle size and distribution. Solvent-catalyst metalmay be included in the diamond feedstock of the different strata inweight percentages of from about 0% to more than about 80%. In someembodiments, diamond feedstock will be loaded with no solvent-catalystmetal in it, relying on sweep of solvent-catalyst metal from thesubstrate to achieve sintering. Use of a plurality of diamond feedstockstrata, the strata having different diamond particle size anddistribution, different solvent-catalyst metal by weight, or both,allows a diamond table to be made that has different physicalcharacteristics at the interface with the substrate than at the loadbearing and articulation surface. This allows a polycrystalline diamondcompact to be manufactured which has a diamond table very firmly bondedto its substrate, and which has very favorable characteristics at theload bearing and articulation surface in order to achieve low frictionarticulation, impact resistance, and durability.

Reduction of Free Volume in Diamond Feedstock

As mentioned earlier, it may be desirable to remove free volume in thediamond feedstock before sintering is attempted. The inventors havefound this is a useful procedure when producing spherical concave andconvex parts. If a press with sufficient anvil travel is used for highpressure and high temperature sintering, however, this step may not benecessary. Preferably free volume in the diamond feedstock will bereduced so that the resulting diamond feedstock is at least about 95%theoretical density and preferably closer to about 97% of theoreticaldensity.

Referring to FIGS. 8 and 8A, an assembly used for precompressing diamondto eliminate free volume is depicted. In the drawing, the diamondfeedstock is intended to be used to make a convex sphericalpolycrystalline diamond part. The assembly may be adapted forprecompressing diamond feedstock for making polycyrstalline diamondcompacts of other complex shapes.

The assembly depicted includes a cube 801 of a pressure transfer medium.A cube is made from pyrophillite or other appropriate pressure transfermaterial such as a synthetic pressure medium and is intended to undergopressure from a cubic press with anvils simultaneously pressing the sixfaces of the cube. A cylindrical cell rather than a cube would be usedif a belt press were utilized for this step.

The cube 801 has a cylindrical cavity 802 or passage through it. Thecenter of the cavity 802 will receive a spherical refractory metal can810 loaded with diamond feedstock 806 that is to be precompressed. Thediamond feedstock 806 may have a substrate with it.

The can 810 consists of two hemispherical can halves 810 a and 810 b,one of which overlaps the other to form a slight lip 812. The can ispreferably an appropriate refractory metal such as niobium, tantalum,molybdenum, etc. The can is typically two hemispheres, one which isslightly larger to accept the other being slid inside of it to fullyenclosed the diamond feedstock. A rebated area or lip is provided in thelarger can so that the smaller can will satisfactorily fit therein. Theseam of the can is sealed with an appropriate sealant such as dryhexagonal boronitride or a synthetic compression medium. The sealantforms a barrier that prevents the salt pressure medium from penetratingthe can. The can seam may also be welded by plasma, laser, or electronbeam processes.

An appropriately shaped pair of salt domes 804 and 807 surround the can810 containing the diamond feedstock 806. In the example shown, the saltdomes each have a hemispherical cavity 805 and 808 for receiving the can810 containing the spherical diamond feedstock 806. The salt domes andthe can and diamond feedstock are assembled together so that the saltdomes encase the diamond feedstock. A pair of cylindrical salt disks 803and 809 are assembled on the exterior of the salt domes 804 and 807. Allof the aforementioned components fit within the bore 802 of the pressuremedium cube 801.

The entire pyrocube assembly is placed into a press and pressurizedunder appropriate pressure (such as about 40-68 Kbar) and for anappropriate although brief duration to precompress the diamond andprepare it for sintering. No heat is necessary for this step.

g. Prepare Heater Assembly

In order to sinter the assembled and loaded diamond feedstock describedabove into polycrystalline diamond, both heat and pressure are required.Heat is provided electrically as the part undergoes pressure in a press.A prior art heater assembly is used to provide the required heat.

A refractory metal can containing loaded and precompressed diamondfeedstock is placed into a heater assembly. Salt domes are used toencase the can. The salt domes used are preferably white salt (NaCl)that is precompressed to at least about 90-95% of theoretical density.This density of the salt is desired to preserve high pressures of thesintering system and to maintain geometrical stability of themanufactured part. The salt domes and can are placed into a graphiteheater tube assembly. The salt and graphite components of the heaterassembly are preferably baked in a vacuum oven at greater than 100degrees Celsius and at a vacuum of at least 23 torr for about 1 hour inorder to eliminate adsorped water prior to loading in the heaterassembly. Other materials which may be used in construction of a heaterassembly include solid or foil graphite, amorphous carbon, pyroliticcarbon, refractory metals and high electrical resistant metals.

Once electrical power is supplied to the heater tube, it will generateheat required for polycrystalline diamond formation in the highpressure/high temperature pressing operation.

h. Preparation of Pressure Assembly for Sintering

Once a heater assembly has been prepared, it is placed into a pressureassembly for sintering in a press under high pressure and hightemperature. A cubic press or a belt press may be used for this purpose,with the pressure assembly differing somewhat depending on the type ofpress used. The pressure assembly is intended to receive pressure from apress and transfer it to the diamond feedstock so that sintering of thediamond may occur under isostatic conditions.

If a cubic press is used, then a cube of suitable pressure transfermedia such as pyrophillite will contain the heater assembly. Cellpressure medium would be used if sintering were to take place in a beltpress. Salt may be used as a pressure transfer media between the cubeand the heater assembly. Thermocouples may be used on the cube tomonitor temperature during sintering. The cube with the heater assemblyinside of it is considered a pressure assembly, and is place into apress a press for sintering.

i. Sintering of Feedstock into Polycrystalline Diamond

The pressure assembly described above containing a refractory metal canthat has diamond feedstock loaded and precompressed within is placedinto an appropriate press. The type of press preferably used at the timeof the invention is a cubic press (i.e., the press has six anvil faces)for transmitting high pressure to the assembly along 3 axes from sixdifferent directions. Alternatively, a belt press and a cylindrical cellcan be used to obtain similar results. Referring to FIG. 8B, arepresentation of the 6 anvils of a cubic press 820 is provided. Theanvils 821, 822, 823, 824, 825 and 826 are situated around a pressureassembly 830.

To prepare for sintering, the entire pressure assembly is loaded into acubic press and initially pressurized to about 40-68 Kbars. The pressureto be used depends on the product to be manufactured and must bedetermined empirically. Then electrical power is added to the pressureassembly in order to reach a temperature preferably in the range of lessthan about 1145 or 1200 to more than about 1500 degrees Celsius.Preferably about 5800 watts of electrical power is available at twoopposing anvil faces, creating the current flow required for the heaterassembly to generate the desired level of heat. Once the desiredtemperature is reached, the pressure assembly is subjected to pressureof about 1 million pounds per square inch at the anvil face. Thecomponents of the pressure assembly transmit pressure to the diamondfeedstock. These conditions are maintained for preferably about 3-12minutes, but could be from less than 1 minute to more than 30 minutes.The sintering of polycrystalline diamond compacts takes place in anisostatic environment where the pressure transfer components arepermitted only to change in volume but are not permitted to otherwisedeform. Once the sintering cycle is complete, about a 90 second cooldown period is allowed, and then pressure is removed. Thepolycrystalline diamond compact is then removed for finishing.

Removal of a sintered polycrystalline diamond compact having a curved,compound or complex shape from a pressure assembly is simple due to thedifferences in material properties between diamond and the surroundingmetals in preferred embodiments of the invention. This is generallyreferred to as the mold release system of the invention.

One or more of the following component processes is incorporated intothe mold release system:

An intermediate layer of material between the polycrystalline diamondcompact part and the mould that prevents bonding of the polycrystallinediamond compact to the mould surface.

A mold material that does not bond to the polycrystalline diamondcompact under the conditions of synthesis.

A mold material that, in the final stages of, or at the conclusion of,the polycrystalline diamond compact synthesis cycle either contractsaway from the polycrystalline diamond compact in the case of a netconcave polycrystalline diamond compact geometry, or expands away fromthe polycrystalline diamond compact in the case of a net convexpolycrystalline diamond compact geometry.

The mold shape can also act, simultaneously as a source of sweep metaluseful in the polycrystalline diamond compact synthesis process.

As an example, below is a discussion of use of a mold release system inmanufacturing a polycrystalline diamond compact by employing a negativeshape of the desired geometry to produce hemispherical cup or races. Themold surface contracts away from the final net concave geometry, themold surface acts as a source of solvent-catalyst metal for thepolycrystalline diamond compact synthesis process, and the mold surfacehas poor bonding properties to polycrystalline diamond compacts.

In the case of forming concave hemispherical cup or races such as areused for articulating surfaces in ball and socket bearing components,two different methods have been employed. In the first method, one, amold consisting of a cobalt chrome (ASTM F-799) ball is used as asubstrate around which a layer of polycrystalline diamond compactfeedstock material is placed, contained by an outer can. A separatorring composed of a material such as mica or compressed hexagonal boronnitride (HBN) is positioned at the hemisphere of the mold ball to allowseparation of the two concave hemispherical polycrystalline diamondcompact parts at the conclusion of the synthesis process. During thepolycrystalline diamond compact synthesis process, the cobalt-chromeball expands in size due to the increase in temperature intrinsic to theprocess. It also can supply solvent-catalyst sweep metal to thepolycrystalline diamond compact synthesis process.

After the polycrystalline diamond compact shell has formed around themold ball, the ball separates from the two hemispherical polycrystallinediamond compact cup or races as it contracts on cooling and pressurereduction. The forces of the shrinking CoCr ball will exceed the bondstrength of diamond to the CoCr, providing a fairly clean separation anda smooth polycrystalline diamond cup or race adjacent a detachedspherical CoCr ball.

As an alternative, it is possible to use an intermediate layer ofmaterial between the polycrystalline diamond compact part and the moldsurface. The intermediate material should be a material which contractsaway from the final net concave polycrystalline diamond compact geometryto achieve mold separation with the polycrystalline diamond compact.

The second mold release method for use in forming a hemispherical cup orrace is similar to the first method. However, in the second method, themold is a cobalt-cemented tungsten carbide ball or sphere that has beencoated with a thin layer of hexagonal boron nitride. During thepolycrystalline diamond compact synthesis process, the tungsten carbideball expands in size due to the increase in temperature intrinsic to theprocess. After the polycrystalline diamond compact shell has formedaround the mold ball, the mold ball separates from the two hemisphericalpolycrystalline diamond compact cup or races as it contracts on cooling.The hexagonal boron nitride prevents bonding between the polycrystallinediamond compact layer and the tungsten carbide ball and a cleanseparation is achieved.

j. Removal of Solvent-Catalyst Metal from PCD

If desired, the solvent-catalyst metal remaining in interstitial spacesof the sintered polycrystalline diamond may be removed. Such removal isaccomplished by chemical leaching as is known in the art. Aftersolvent-catalyst metal has been removed from the interstitial spaces inthe diamond table, the diamond table will have greater stability at hightemperatures. This is because there is no catalyst for the diamond toreact with and break down. Removal of solvent-catalyst metal frominterstitial spaces in the diamond may also be desirable if thesolvent-catalyst material is not biocompatible.

After leaching solvent-catalyst metal from the diamond table, it may bereplaced by another metal, metal or metal compound in order to formthermally stable diamond that is stronger than leached polycrystallinediamond. If it is intended to weld synthetic diamond or apolycrystalline diamond compact to a substrate or to another surfacesuch as by inertia welding, it may be desirable to use thermally stablediamond due to its resistance to heat generated by the welding process.

3. Finishing Methods and Apparatuses

Once a polycrystalline diamond compact has been sintered, a mechanicalfinishing process is preferably employed to prepare the final product.The preferred finishing steps explained below are described with respectto finishing a polycrystalline diamond compact, but they could be usedto finish any other bearing surface or any other type of component.

Prior to the invention herein, the synthetic diamond industry was facedwith the problem of finishing flat surfaces and thin edges of diamondcompacts. Methods for removal of large amounts of diamond from sphericalsurfaces or finishing those surfaces to high degrees of accuracy forsphericity, size and surface finish had not been developed in the priorart.

a. Finishing of Superhard Cylindrical and Flat Forms

In order to provide a greater perspective on the most preferredfinishing techniques for curved and spherical superhard surfaces, adescription of other finishing techniques is provided.

1. Lapping

A wet slurry of diamond grit on cast iron or copper rotating plates areused to remove material on larger flat surfaces (e.g., up to about 70mm. in diameter). End coated cylinders of size ranging from about 3 mmto about 70 mm may also be lapped to create flat surfaces. Lapping isgenerally slow and not dimensionally controllable for depth and layerthickness, although flatness and surface finishes can be held to veryclose tolerances.

2. Grinding

Diamond impregnated grinding wheels are used to shape cylindrical andflat surfaces. Grinding wheels are usually resin bonded in a variety ofdifferent shapes depending on the type of material removal required(i.e., cylindrical centerless grinding or edge grinding).Polycrystalline diamond compacts are difficult to grind, and largepolycrystalline diamond compact surfaces are nearly impossible to grind.Consequently, it is desirable to keep grinding to a minimum, andgrinding is usually confined to a narrow edge or perimeter or to thesharpening of a sized PDC end-coated cylinder or machine tool insert.

3. Electro Spark Discharge Grinding (EDG)

Rough machining of polycrystalline diamond compact may be accomplishedwith electro spark discharge grinding (“EDG”) on large diameter (e.g.,up to about 70 mm.) flat surfaces. This technology typically involvesthe use of a rotating carbon wheel with a positive electrical currentrunning against a polycrystalline diamond compact flat surface with anegative electrical potential. The automatic controls of the EDG machinemaintain proper electrical erosion of the polycrystalline diamondcompact material by controlling variables such as spark frequency,voltage and others. EDG is typically a more efficient method forremoving larger volumes of diamond than lapping or grinding. After EDG,the surface must be finish lapped or ground to remove what is referredto as the heat affected area or re-cast layer left by EDG.

4. Wire Electrical Discharge Machining (WEDM)

WEDM is used to cut superhard parts of various shapes and sizes fromlarger cylinders or flat pieces. Typically, cutting tips and inserts formachine tools and re-shaping cutters for oil well drilling bitsrepresent the greatest use for WEDM in PDC finishing.

5. Polishing

Polishing superhard surfaces to very high tolerances may be accomplishedby diamond impregnated high speed polishing machines. The combination ofhigh speed and high friction temperatures tends to burnish a PDC surfacefinished by this method, while maintaining high degrees of flatness,thereby producing a mirror-like appearance with precise dimensionalaccuracy.

b. Finishing a Spherical Geometry.

Finishing a spherical surface (concave spherical or convex spherical)presents a greater problem than finishing a flat surface or the roundededge of a cylinder. The total surface area of a sphere to be finishedcompared to the total surface area of a round end of a cylinder of likeradius is four (4) times greater, resulting in the need to remove four(4) times the amount of polycrystalline diamond compact material. Thenature of a spherical surface makes traditional processing techniquessuch as lapping, grinding and others unusable because they are adaptedto flat and cylindrical surfaces. The contact point on a sphere shouldbe point contact that is tangential to the edge of the sphere, resultingin a smaller amount of material removed per unit of time, and aproportional increase in finishing time required. Also, the design andtypes of processing equipment and tooling required for finishingspherical objects must be more accurate and must function to closertolerances than those for other shapes. Spherical finishing equipmentalso requires greater degrees of adjustment for positioning theworkpiece and tool ingress and egress.

The following are steps that may be performed in order to finish aspherical, rounded or arcuate surface.

1. Rough Machining

It is preferred to initially rough out the dimensions of the surfaceusing a specialized electrical discharge machining apparatus. Referringto FIG. 9, roughing a polycrystalline diamond compact sphere 903 isdepicted. A rotator 902 is provided that is continuously rotatable aboutits longitudinal axis (the z axis depicted). The sphere 903 to beroughed is attached to a spindle of the rotator 902. An electrode 901 isprovided with a contact end 901A that is shaped to accommodate the partto be roughed. In this case the contact end 901A has a partiallyspherical shape. The electrode 901 is rotated continuously about itslongitudinal axis (the y axis depicted). Angular orientation of thelongitudinal axis y of the electrode 901 with respect to thelongitudinal axis z of the rotator 902 at a desired angle β is adjustedto cause the electrode 901 to remove material from the entire sphericalsurface of the ball 903 as desired.

Thus, the electrode 901 and the sphere 903 are rotating about differentaxes. Adjustment of the axes can be used to achieve near perfectspherical movement of the part to be roughed. Consequently, a nearlyperfect spherical part results from this process. This method producespolycrystalline diamond compact spherical surfaces with a high degree ofsphericity and cut to very close tolerances. By controlling the amountof current introduced to the erosion process, the depth and amount ofthe heat affected zone can be minimized. In the case of apolycrystalline diamond compact, the heat affected zone can be kept toabout 3 to 5 microns in depth and is easily removed by grinding andpolishing with diamond impregnated grinding and polishing wheels.

Referring to FIG. 10, roughing a convex spherical polycrystallinediamond compact 1003 such as an acetablular cup or race is depicted. Arotator 1002 is provided that is continuously rotatable about itslongitudinal axis (the z axis depicted). The part 1003 to be roughed isattached to a spindle of the rotator 1002. An electrode 1001 is providedwith a contact end 1001A that is shaped to accommodate the part to beroughed. The electrode 1001 is continuously rotatable about itslongitudinal axis (the y axis depicted). Angular orientation of thelongitudinal axis y of the electrode 1001 with respect to thelongitudinal axis z of the rotator 1002 at a desired angle β is adjustedto cause the electrode 1001 to remove material from the entire sphericalsurface of the cup or race 1003 as desired.

In some embodiments of the invention, multiple electro discharge machineelectrodes will be used in succession in order to machine a part. Abattery of electro discharge machines may be employed to carry this outin assembly line fashion.

2. Finish Grinding and Polishing

Once the spherical surface (whether concave or convex) has been roughmachined as described above or by other methods, finish grinding andpolishing of a part can take place. Grinding is intended to remove theheat affected zone in the polycrystalline diamond compact material leftbehind by electrodes. Use of the same rotational geometry as depicted inFIGS. 9 and 10 allows sphericity of the part to be maintained whileimproving its surface finish characteristics.

Referring to FIG. 11, it can be seen that a rotator 1101 holds a part tobe finished 1103, in this case a convex sphere, by use of a spindle. Therotator 1101 is rotated continuously about its longitudinal axis (the zaxis). A grinding or polishing wheel 1102 is provided is rotatedcontinuously about its longitudinal axis (the x axis). The moving part1103 is contacted with the moving grinding or polishing wheel 1102. Theangular orientation β of the rotator 1101 with respect to the grindingor polishing wheel 1102 may be adjusted and oscillated to effectgrinding or polishing of the part (ball or socket) across its entiresurface and to maintain sphericity.

Referring to FIG. 12, it can be seen that a rotator 1201 holds a part tobe finished 1203, in this case a convex spherical cup or race, by use ofa spindle. The rotator 1201 is rotated continuously about itslongitudinal axis (the z axis). A grinding or polishing wheel 1202 isprovided that is continuously rotatable about its longitudinal axis (thex axis). The moving part 1203 is contacted with the moving grinding orpolishing wheel 1202. The angular orientation β of the rotator 1201 withrespect to the grinding or polishing wheel 1202 may be adjusted andoscillated if required to effect grinding or polishing of the partacross the spherical portion of it surface.

In the preferred embodiment of the invention, grinding utilizes a gritsize ranging from 100 to 150 according to standard ANSI B74.16-1971 andpolishing utilizes a grit size ranging from 240 to 1500, although gritsize may be selected according to the user's preference. Wheel speed forgrinding should be adjusted by the user to achieve a favorable materialremoval rate, depending on grit size and the material being ground. Asmall amount of experimentation can be used to determine appropriatewheel speed for grinding.

As desired in the invention, a diamond abrasive hollow grill may be usedfor polishing diamond or superhard bearing surfaces. A diamond abrasivehollow grill includes a hollow tube with a diamond matrix of metal,ceramic and resin (polymer) is found.

If a diamond surface is being polished, then the wheel speed forpolishing preferably will be adjusted to cause a temperature increase orheat buildup on the diamond surface. This heat buildup will causeburnishing of the diamond crystals to create a very smooth andmirror-like low friction surface. Actual material removal duringpolishing of diamond is not as important as removal sub-micron sizedasperities in the surface by a high temperature burnishing action ofdiamond particles rubbing against each other. A surface speed of 6000feet per minute minimum is generally required together with a highdegree of pressure to carry out burnishing. Surface speeds of 4000 to10,000 feet per minute are believed to be the most desirable range.

Depending on pressure applied to the diamond being polished, polishingmay be carried out at from about 500 linear feet per minute and 20,000linear feet per minute.

Pressure must be applied to the workpiece in order to raise thetemperature of the part being polished and thus to achieve the mostdesired mirror-like polish, but temperature should not be increased tothe point that it causes complete degradation of the resin bond thatholds the diamond polishing wheel matrix together, or resin will bedeposited on the diamond. Excessive heat will also unnecessarily degradethe surface of the diamond.

Maintaining a constant flow of coolant (such as water) across thediamond surface being polished, maintaining an appropriate wheel speedsuch as 6000 linear feet per minute, applying sufficient pressureagainst the diamond to cause heat buildup but not so much as to degradethe wheel or damage the diamond, and timing the polishing appropriatelyare all important and must all be determined and adjusted according tothe particular equipment being used and the particular part beingpolished. Generally the surface temperature of the diamond beingpolished should not be permitted to rise above 800 degrees Celsius orexcessive degradation of the diamond will occur. Desirable surfacefinishing of the diamond, called burnishing, generally occurs between650 and 750 degrees Celsius.

During polishing it is important to achieve a surface finish that hasthe lowest possible coefficient of friction, thereby providing a lowfriction and long-lasting articulation surface. Preferably, once adiamond or other superhard surface is formed in a bearing component, thesurface is then polished to an Ra value of 0.3 to 0.005 microns.Acceptable polishing will include an Ra value in the range of 0.5 to0.005 microns or less. The parts of the bearing component may bepolished individually before assembly or as a unit after assembly. Othermethods of polishing polycrystalline diamond compacts and othersuperhard materials could be adapted to work with the articulationsurfaces of the invented bearing components, with the objective being toachieve a smooth surface, preferably with an Ra value of 0.01-0.005microns.

Referring to FIG. 13, a polycrystalline diamond compact bearing 1302 isbeing ground to spherical form and dimensions using a centerlessgrinding machine 1301. The bearing 1302 rests on a support rail 1305 andis kept in contact with a rotating diamond grinding wheel 1303 by arubber composite regulating wheel 1304. The rotational motion of thegrinding wheel 1303 and the regulating wheel 1304 cause the bearing 1302to rotate against the surface of the grinding wheel 1303. The regulatingwheel 1304, having a large frictional component because of its softplastic surface, rotates the ball 1302 at high velocity and causes theball 1302 to be pressed against the diamond grinding wheel 1303 withconsiderable pressure and thus effects removal of material from thesurface of ball 1302 by abrasion. The small tangential contact pointbetween the diamond grinding wheel 1303 and the ball 1302 causes highpoints on the ball 1302 to grind readily, and as the ball 1302 movesback and forth along the rail 1305, crossing paths are ground on thesurface of the ball 1302. The feed rate of the regulating wheel 1304toward the diamond grinding wheel 1303 determines the width of theground path on the surface of the diamond ball 1302. High rates offeeding, such as 0.001 inch per minute generates a much wider path thana slower rate such as 0.0001 inch per minute. Therefore, roughing ratesmay vary from 0.0001 to 0.0040 and finishing rates from 0.00003 to0.0005 inch per minute, or as otherwise selected by the user. Theregulating wheel 1304 and the diamond grinding wheel 1303 may bemodified with spiral grooves to facilitate the horizontal movement androtation of the ball 1302 along the rail 1305. Those familiar with theart of centerless grinding can readily appreciate the variousmethodologies, machine settings and grinding wheel types useful forgrinding diamond balls.

Structures manufactured according to the principles of the invention setforth above will provide strong and durable low friction bearingsurfaces for a variety of uses including bearing components.

While the present invention has been described and illustrated inconjunction with a number of specific embodiments, those skilled in theart will appreciate that variations and modifications may be madewithout departing from the principles of the invention as illustratedherein and as claimed. The present invention may be embodied in otherspecific forms without departing from its spirit or essentialcharacteristics. The described embodiments are to be considered in allrespects as only illustrative, and not restrictive. The scope of theinvention is, therefore, indicated by the appended claims, rather thanby the foregoing description. All changes that come within the meaningand range of equivalency of the claims are to be embraced within theirscope.

1-57. (canceled)
 58. A bearing comprising: a race having an articulationsurface; a plurality of roller elements, each roller element having anarticulation surface; wherein the plurality of roller elements areconfigured for rolling across the articulation surface of said race; andwherein at least one of said race and said roller elements comprises asintered compact of superhard material forming the articulation surfacethereof.
 59. A bearing as recited in claim 58, wherein at least one ofthe race and the plurality of roller elements is formed from acontinuous phase of polycrystalline diamond.
 60. A bearing as recited inclaim 58, further comprising a second race configured for rollingengagement with said plurality of roller bearing elements.
 61. A bearingas recited in claim 60 wherein the second race articulation surfacecomprises sintered polycrystalline diamond.
 62. A bearing as recited inclaim 58, wherein the race and the plurality of roller elements comprisesintered polycrystalline diamond.
 63. A bearing comprising: a firstrace, the first race having an articulation surface which comprises asintered compact of superhard material selected from the groupconsisting of diamond and boron nitride; and a plurality of bearingroller elements, each of the plurality of bearing roller elementscomprising an articulation surface which comprises a sintered compact ofsuperhard material selected from the group consisting of diamond andboron nitride, and wherein the bearing roller elements roll across thefirst race articulation surface.
 64. The bearing of claim 63, whereinthe first race comprises a compact having a substrate and having thesuperhard material bonded to the surface of the substrate.
 65. Thebearing of claim 64, wherein only a portion of the race articulationsurface is covered with the superhard material.
 66. The bearing of claim63, wherein the each of the plurality of bearing roller elementscomprise a compact having a substrate and having the superhard materialbonded to the surface of the substrate.
 67. The bearing of claim 66,wherein only a portion of the bearing roller element articulationsurface is covered with superhard material.
 68. The bearing of claim 63,wherein each of the bearing roller elements has a circular crosssection.
 69. The bearing of claim 63, wherein each of the bearing rollerelements is spherical.
 70. The bearing of claim 63, further comprising asecond race, the second race having an articulation surface whichcomprises a sintered compact of superhard material selected from thegroup consisting of diamond and boron nitride, and wherein the pluralityof bearing roller elements roll across the second race articulationsurface.
 71. The bearing of claim 70, wherein the first race and thesecond race are disposed about a common axis of rotation such that thefirst race articulation surface faces towards the second racearticulation surface and such that the plurality of bearing rollerelements are disposed therebetween, and wherein each of the plurality ofbearing roller element is in contact with the first race articulationsurface and the second race articulation surface.
 72. The bearing ofclaim 71, wherein the first race is rotatable about the common axisrelative to the second race, and wherein the plurality of bearing rollerelements roll between the first race and second race.
 73. A bearingcomprising: a plurality of bearing roller elements, each of theplurality of bearing roller elements comprising an articulation surfacewhich is formed from a sintered compact of superhard material selectedfrom the group consisting of diamond and boron nitride; a first race,the first race comprising a first circular articulation surface which isformed from a sintered compact of superhard material selected from thegroup consisting of diamond and boron nitride; and a second race, thesecond race comprising a second circular articulation surface which isformed from a sintered compact of superhard material selected from thegroup consisting of diamond and boron nitride; and wherein the firstrace and second race are disposed about a common rotational axis andwherein the plurality of bearing roller elements are disposed betweenthe first circular articulation surface and the second circulararticulation surface and in contact with the first circular articulationsurface and second circular articulation surface, and wherein theplurality of bearing roller elements roll across the first circulararticulation surface and the second circular articulation surface tofacilitate the rotation of the first race relative to the second race.74. The bearing of claim 73, wherein the first circular articulationsurface and second circular articulation surface comprises a continuouslayer of superhard material.
 75. The bearing of claim 73, wherein thefirst circular articulation surface comprises segmented superhardmaterial.
 76. The bearing of claim 73, wherein the first race comprisesa compact having a substrate and having the superhard material attachedto the surface of the substrate.
 77. The bearing of claim 76, whereinthe substrate comprises metal, metal carbides, and mixtures thereof. 78.The bearing of claim 73, wherein the superhard material comprises bondedparticles of superhard material and metal located between said particlesof superhard material.